Lanthanum Strontium Manganite Research Articles

The effectiveness of titanium ions toward crystal structure, microstructure and optical properties of La0.5Sr0.5Mn1-xTixO3 nanopowders

Titanium subrogated lanthanum strontium manganite LSMO (La0.5Sr0.5Mn1-xTixO3; Ti ratio = 0.1, 0.2, 0.3, 0.4, 0.5) nanoparticles have been prepared based on an organic acid precursor pathway using glycine-nitrate as a fuel. The effectuation of Ti4+ ion concentration on the crystallo-aspects, microstructure as well as the optical features was scrutinized. Exemplary, orthorhombic perovskite LSMTO with a space group Pbnm were manifested at low annealing temperature 800 °C for period 2h. Further, insertion of Ti4+ ion instead of Mn4+ ion in LSMO commenced to increment the crystallite size from 14 to 24 nm. The FT-IR spectrum demonstrated that band around 600 cm−1 linked to Mn-O become broad imputed to Ti-O stretching modes. The morphology of all samples presented the spherical clusters with enhancing the grain size by incorporation of Ti4+ ion into the LSMO crystal. Band gap energy with boost of Ti4+ ion weight ratio was found to augment from 1.83 to 2.1 eV. Meanwhile, the refractive index was found to slightly minify from 2.78 to 2.66.

Role of Gd3+ on the magnetocaloric properties of lanthanum-strontium manganite

In this work, the role of magnetic ion Gd3+ in the crystal structure, magnetic and magnetocaloric properties of doped lanthanum-strontium manganite (La0.7-xGdxSr0.3MnO3 varying x from 0 to 0.2) synthesized by high-energy ball milling assisted with annealing, is discussed. Furthermore, the interplay between the magnetic and crystal structure in co-doped manganites is proposed. The X-ray diffraction patterns confirm the complete formation of lanthanum manganite showing different crystal structures regarding the gadolinium content. The Sr2+/Gd3+ doped lanthanum manganites with Gd3+ concentration lower than 0.1 mol show rhombohedral crystal structure (R-3cH). Higher gadolinium concentrations promote a phase transition from rhombohedral to orthorhombic crystal structure. The Curie temperature of the manganites decreases with an increase in Gd3+ content, from 376 K to 257 K, for un-doped and x = 0.2 Gd3+, respectively, attributed to a weakening in the double exchange interaction. Close interaction of the lattice parameters such as bond distances, bond angles, and symmetry-related with the mixed magnetic interactions was observed. The maximum magnetocaloric effect (MCE) calculated using Maxwelĺs ratio was observed around the paramagnetic to ferromagnetic ordering, at 311 K, for gadolinium content of 0.15 mol, measured through the entropy change. The Sr2+/Gd3+ doped lanthanum manganite shows a magnetically induced entropy change (|ΔSM|) in the range from 2.4 to 3.69 Jkg-1K−1 under 18 kOe, for 0.10 and 0.15, respectively, doing this manganite a suitable material for refrigeration applications at room temperature.

Synthesis and characterization of nickel doped LSM as possible cathode materials for LT-SOFC application

Doping lanthanum strontium manganite with Ni2+ at Mn site for 10–30 mol% was investigated as cathode material for LT-SOFC application. Nanopowders were prepared using a simple solution combustion technique and only after calcination at 1200 °C phase purity was obtained. While TEM analysis confirmed particle size around 30 nm, the DLS study showed average most probable size as 13 nm. The SEM-EDAX analysis revealed porous nanopowder of all the studied compositions. It also confirmed composition of the cathode material. In symmetric cell configuration, using lanthanum gallate as electrolyte, oxygen reduction reaction (ORR) and hence polarization resistance (RP) was studied in detail in the temperature range 500–800 °C. The composition La0.7Sr0.3Mn0.8Ni0.2O3 (LSMN7382) showed lowest RP value of 0.117–0.039 Ω-cm2 in the temperature range 500–800 °C. In contrast, La0.7Sr0.3MnO3 (LSM731) showed much higher RP value. Among the cathodes with Sr2+doping variation in La site, 30 mol% showed the best performance. The electrical conductivity of ∼80% dense electrolyte pellets were studied and highest conductivity of 70 S/cm at 800 °C was observed for LSMN7382 among the all compositions. Generation of hole takes place due to the charge compensation in Mn3+ to Mn4+ conversion while doping Sr2+ as well as Ni2+. At 30 mol% Ni2+ doping (LSMN7373), the decrease of conductivity may be attributed to the secondary phase formation. A detailed electrical circuit analysis of the impedance spectrum indicates that charge transfer polarization resistance is the key to control the interface performance. Such high ORR performance by nickel doping can be explained due to Mn4+ converted to Mn3+ at high temperature and thus creating oxygen vacancy to enhance ORR ionic path on the cathode surface.

Sensor for operational control of oxygen and combustible gases concentration in waste gases of thermal units

A new sensor has been developed for continuous monitoring of oxygen and combustible gases content in the waste gases of thermal units. The target application of the sensor is its installation in shunt pipes of thermal units, directly into the waste gas flow. The sensor is characterized by one reference gas electrode and three measuring electrodes applied on the surface of a solid electrolyte tube made of a zirconia electrolyte (e.g., 8YSZ). The reference gas electrode and one of the measuring electrodes were made of silver, the second measuring electrode was made of platinum, the third measuring electrode was made of a mixture of zinc oxide (95 wt %) and lanthanum-strontium manganite (5 wt %). The oxygen content in the gas mixture was determined by the well-known potentiometric method in accordance with the Nernst equation, i.e. an Ag|8YSZ|Ag electrochemical cell was used. To determine the products of incomplete combustion of fuel, the method of mixed potential between Pt- and Zn-based electrodes was used; the obtained potential value was determined by the difference in the oxidation rate of carbon monoxide as the main component of unburned fuels, on different materials of measuring electrodes. The experimental results of the sensor for the determination of carbon monoxide, hydrogen, and methane in a gas mixture are presented.

Evolution of the surface atomic structure of multielement oxide films: curse or blessing?

Atomically resolved scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are used to gain atomic-scale insights into the heteroepitaxy of lanthanum-strontium manganite (LSMO, La1-xSrxMnO3-δ, x ≈ 0.2) on SrTiO3(110). LSMO is a perovskite oxide characterized by several composition-dependent surface reconstructions. The flexibility of the surface allows it to incorporate nonstoichiometries during growth, which causes the structure of the surface to evolve accordingly. This happens up to a critical point, where phase separation occurs, clusters rich in the excess cations form at the surface, and films show a rough morphology. To limit the nonstoichiometry introduced by non-optimal growth conditions, it proves useful to monitor the changes in surface atomic structures as a function of the PLD parameters and tune the latter accordingly.

Fabrication and optimization of LSM infiltrated cathode electrode for anode supported microtubular solid oxide fuel cells

In this study, anode supported microtubular solid oxide fuel cells (SOFCs) with LSM (lanthanum strontium manganite) catalyst infiltrated LSM-YSZ (yttria stabilized zirconia) cathodes are developed to increase the density of triple/three phase boundaries (TPBs) in the cathode, thereby to improve the cell performance. For this purpose, two different porous YSZ layers are formed on the dense YSZ electrolyte, i.e., one is with co-sintering while the other one is not. Incorporation of LSM into these porous YSZ layers is achieved via dip coating of a sol-gel based infiltration solution. The effects of the fabrication method for porous YSZ, LSM solution dwelling time and the thickness of the porous YSZ layer on the cell performance are experimentally investigated and optimized in the given order. A reference cell having a conventional dip coated cathode prepared by mixing the commercial LSM and YSZ powders is also fabricated for comparison. The results show that among the cases considered, the highest peak power density of 0.828 W/cm2 can be obtained from the cell, whose single dip coated porous electrolyte layer co-sintered with the dense electrolyte is impregnated with LSM for a dwelling time of 45 min. On the other hand, the peak power density of the reference cell is measured as only 0.558 W/cm2. These results reveal that ∼50% increase in the maximum cell performance compared to that of the reference cell can be achieved by LSM infiltration after the optimizations.

Weight Change Mechanism of Lanthanum Strontium Manganite (LSM) During Thermal Cycles

Weight Change Mechanism of Lanthanum Strontium Manganite (LSM) During Thermal Cycles

Solid Oxide Fuel Cells with 3D Inkjet Printing Modified LSM-YSZ Interface

Solid oxide fuel cells (SOFCs) have drawn attention as an alternative power generation technology due to demonstrated high efficiency and low emissions. The lanthanum strontium manganite (LSM)-yttria-stabilized zirconia (YSZ) cathode is utilized widely for SOFCs due to its high performance and stability. The electrochemical oxygen reduction reaction that occurs in the cathode can be enhanced by the porous LSM-YSZ cathode with good electronic and ionic conductivity. With sufficient electrochemically active reaction sites, the oxygen ion transfer processes in the mixed ionic conductor (YSZ) and at the interface of cathode and electrolyte (LSM-YSZ) become critical for the activity of the cathode. Thus, the pillar shape YSZ microstructure with ~ 150 μm×150 μm×10 μm (L×W×H) size can be fabricated by 3D inkjet printing on the interface of electrolyte and cathode to increase the TPB area and enhance the connection between the dense YSZ electrolyte and mixed YSZ ionic conductor. Scanning Electron Microscopy (SEM) is utilized to assess the morphology and microstructure of the YSZ interface. To investigate the influence of the modified interface on the performance of the SOFC, electrochemical performance testing and characterization are conducted for the SOFCs with/without the modified YSZ layer. The microstructures with different pillar central spacing are also fabricated by 3D inkjet printer to optimize the geometry of the LSM-YSZ interface.

Investigation of Heat Distribution in SOC-Stacks By Multiphysical Modeling

In the scope of clean energy, the solid oxide cell (SOC) offers a promising solution for different applications. The electrolyte, the air electrode and the fuel electrode of an SOC are typically based on yttrium stabilized zirconia (YSZ), lanthanum strontium cobaltite (LSC) or manganite (LSM) and nickel cermet, respectively. It typically operates in a temperature range of 600 – 1000 oC and can be operated as a fuel cell (SOFC), an electrolysis cell (SOEC) or reversibly (rSOC).An SOC-stacks consists of several repeating units, each of which is assembled by various components. Among them, the sealants are important to maintain the reliability and long-term operations of a stack. Several issues lead to high stress in the sealants, including the mechanical load, mismatch of thermal expansion coefficients, and thermal gradients 1. It was indicated that a small temperature gradient near the manifolds results in excessively high tensile stress. This may lead to glass ceramics sealing failure, which is critical in SOC designs 2. Therefore, the authors carry out the elastic stress simulations in an operating SOC-stack due to non-uniform temperature distributions.A previously introduced CFD model 3 is further developed to address coupled chemical and electrochemical reactions in rSOC-stacks. This model has been implemented in the open-source library, OpenFOAM. It considers the major multiphysical phenomena e.g. heat, mass, momentum and charge transport as well as heat radiation and electrochemical reactions and employs a volume-averaged approach 4. The computational requirements can be greatly reduced, which offers the possibility to simulate large stacks in reduced computing time. The temperature distributions derived from the stack simulation are used as inputs for thermal stress analysis, by mapping the interconnect temperatures to the detailed repeating unit. An open-source, finite element method (FEM) based software, Calculix, is applied to simulate the stress distributions. It is assumed all layers are tightly connected without slipping.The SOC-stack design considered in the multiphysical simulation as well as the FEM stress analysis is an in-house design, Mark-F20. It consists of 18 repeating units, each with an active area of approximately 320 cm2. The stack operates in the furnace condition, at a temperature of 700 oC, with CH4 mixture being supplied to the anode in the SOFC-mode (i=0.5 A/cm², U=0.8 V). The flow is in a counter-flow regime. A comparison of temperature distributions in interconnect is conducted between simulation and experiment. A maximum deviation of 10 K can be observed near the fuel inlet. It is acceptable providing the overall temperature variations of 80 K and the uncertainties in the measurements. This low-temperature zone results from the fast endothermic methane steam reforming reaction. The zone near the fuel outlet is cooled down by the inlet airflow on the cathode side. The stress-free temperature is 800 oC. It can be found that the maximum stress appears around the fuel inlet manifold with a magnitude of 100 MPa. The stress is also large near the air inlet manifold with a magnitude of 70 MPa. These areas show higher possibilities of mechanical failure.Consequentially, the stack model that has been developed enables to investigate the heat distribution in SOC-stacks. By comparing temperature distribution and the IV-curve predicted by the model with experimental measurements, good agreements were found.In the future, the sealant failure will be investigated 2 and attention has to be paid to future stack designs. References(1) Blum, L.; Groß, S. M.; Malzbender, J.; Pabst, U.; Peksen, M.; Peters, R.; Vinke, I. C. Investigation of Solid Oxide Fuel Cell Sealing Behavior under Stack Relevant Conditions at Forschungszentrum Jülich. Journal of Power Sources 2011, 196 (17), 7175–7181.(2) Bremm, S.; Dölling, S.; Becker, W.; Blum, L.; Peters, Ro.; Malzbender, J.; Stolten, D. A Methodological Contribution to Failure Prediction of Glass Ceramics Sealings in High-Temperature Solid Oxide Fuel Cell Stacks. Journal of Power Sources 2021, 507, 230301.(3) Zhang, S.; Peters, R.; Varghese, B. A.; Deja, R.; Kruse, N.; Beale, S. B.; Blum, L.; Peters, R. Modeling of Reversible Solid Oxide Cell Stacks with an Open-Source Library. ECS Trans. 2021, 103 (1), 569.(4) Beale, S. B.; Zhubrin, S. V. A Distributed Resistance Analogy for Solid Oxide Fuel Cells. Numerical Heat Transfer, Part B: Fundamentals 2005, 47, 573–591. Figure 1

Reticulated porous lanthanum strontium manganite structures for solar thermochemical hydrogen production

Porous ceramic foams are utilized in various fields and applications due to their advantageous properties such as high porosity, high specific surface area, and controlled permeability. Non-stoichiometric oxide foams are of particular interest for the solar thermochemical production of hydrogen in directly irradiated solar receivers due to their enhanced heat transfer capabilities and structural integrity. We report the fabrication of lanthanum strontium manganite replica foams and their solar thermochemical water splitting performance. Highly porous (>80%) foams were produced with controlled structure and tested in a high temperature water splitting furnace to demonstrate stability and overall performance. The temperature profile of the burnout and sintering of the foam structure were altered based on simultaneous differential scanning calorimetry and thermal gravimetry analysis. Two-step sintering was used both to retain micron-sized pores (D50 = 0.4 μm) on the foam's struts and to limit grain growth to a grain size of ∼1 μm. The structural characteristics were confirmed by porosimetry and scanning electron microscopy. The foams were repeatedly cycled, producing approximately 200 μmol/g of H2 per cycle. Water splitting performance was tested for 50 cycles and approximately 35 h at 1400 °C. No statistical difference in the effective hydrogen production per cycle was observed, which is promising for long-term redox cycle stability.

Predicting optimal geometries of 3D-printed solid oxide electrochemical reactors

Solid oxide electrochemical reactors (SOERs) may be operated in fuel cell (SOFC) or electrolyser (SOE) modes, at temperatures > 800 K, depending on electrolyte and electrode materials. In electrolyser mode, current densities of ≥ ca. 104 A m−2 are achievable at potential differences ideally at the thermoneutral values of 1.285 V for steam splitting or 1.46 V for CO2 splitting at 750 °C. As for large scale chemical processes in general, such reactors are required to be energy efficient, economic, of scalable design and fabrication, and durable ideally over ≥ ca. 10 years.Increasing densities of electrode | electrolyte interfacial areas (and electrode | electrolyte | pore triple phase boundaries) of solid oxide fuel cells or electrolysers offers one means of increasing performance, reproducibility, durability and potentially decreasing cost. Three-dimensional structuring of those interfaces can be achieved by 3D printing, but modelling is required to optimise geometries. Using kinetic parameter values from the literature, COMSOL Multiphysics® finite element software was used to predict effects of 3D geometries, increasing interfacial to geometric area ratios, on SOER performances for YSZ ((ZrO2)0.92(Y2O3)0.08) oxide ion conducting electrolyte and Ni-YSZ electrode based cells, relative to corresponding planar structures with < 10 μm thick planar YSZ electrolyte. For the negative electrode, electrolyte and electrode layers were inkjet printed on Ni(O)-YSZ substrate precursors, then sintered. For the positive electrode, porous lanthanum strontium manganite (LSM: La0.8Sr0.2MnO3-δ) was brush-coated over the (gas-tight) YSZ, then sintered to produce complete SOERs: H2O-H2 | Ni(O)-YSZ | YSZ-YSZ pillars | YSZ-LSM | LSM | O2.Results are reported showing that, in the case of solid YSZ pillars, despite interfacial electrode | electrolyte areas being up scaled by factors of 10–150 depending on height (10–150 μm), current densities were predicted to increase by only ca. 1.14 in electrolysis mode and peak power densities were predicted to increase by ca. 1.93 in fuel cell mode. This was due to increased ionic current path length along the pillars, increasing ohmic potential losses relative to faradaic impedances; as expected, such predictions depend strongly on electrode kinetic parameter values. After sintering the porous Ni(O)-YSZ pillars and their subsequent reduction with H2 to nickel, they were assumed to constitute equipotential surfaces, depending on current collector design. Predicted current densities were up to 1011 mA cm−2, far greater than in solid YSZ pillars, ultimately limited by reactant or product mass transport through porous pillars of increasing height.

3-D inkjet printed solid oxide electrochemical reactors III. Cylindrical pillared electrode microstructures

Inkjet printing is a scalable technique that can fabricate customised three-dimensional microstructures, reproducibly, accurately, and with high material utilisation, by printing multiple layers sequentially onto previously printed layers, to produce architectures tailored in this case to electrochemical reactors.Printable yttria-stabilised zirconia (YSZ) and lanthanum strontium manganite (LSM) inks were formulated to enable fabrication of solid oxide electrochemical reactors (SOERs): H2O-H2 | Ni(O)-YSZ | YSZ | YSZ pillars | LSM | O2. Of the geometries studied, equi-sized, hexagonally-arranged cylindrical pillars were predicted to produce the largest ratio of interfacial to geometric (cross-sectional) areas. However, this neglects effects of potential and current density distributions that constrain up-scaling to more modest factors. Hence, using kinetic parameter values from the literature, finite element computational simulations of the pillared SOER in (H2 - O2) fuel cell mode predicted peak power densities of 0.11 W cm−2 at 800 °C, whereas its counterpart with only a planar electrolyte layer produced only 0.05 W cm−2; i.e. the pillars were predicted to enhance peak power densities by ca. 2.3.Arrays of several thousand YSZ cylindrical pillars were printed, with post-sintering diameter, height, and spacing of 25, 95 and 63 μm, respectively. LSM was inkjet-printed onto the pillars, and sintered subsequently, to produce contiguous films ca. 4 μm thick. In (H2 - O2) fuel cell mode at 725, 770, and 795 °C, these reactors produced peak power densities of 0.09, 0.21, 0.30 W cm−2, respectively, 3–6 times greater than the performance of ‘benchmark’ Ni(O)-YSZ | YSZ | LSM reactors inkjet-printed with planar cathodes operating under the same conditions, thereby demonstrating the benefit of inkjet printing as a fabrication technique for SOERs.

Electrical Conductivity of LSM—YSZ Oxygen Electrode for Determining Active Electrode Zone in Solid Oxide Cells

Solid oxide cells (SOCs) show high potential in applications related to sustainable society. The substantial contribution of the SOCs is their high efficiency in terms of the electric energy utilization due to the operating temperature up to 800 °C. The effect of high operation temperature is favorable in two ways. Firstly, it accelerates the kinetics of electrochemical reactions preventing the need of the use of Pt-based catalysts. Secondly, the high temperature offers favorable thermodynamic conditions decreasing the equilibrium potential for water splitting. This makes the SOCs technology a direct competitor to low-temperature technologies, such as alkaline or PEM electrolysis.The SOCs are composed of electrolyte, fuel electrode and oxygen electrode. The electrolyte allows transport of oxygen ions between the electrodes due to its high ionic conductivity. Yttria-stabilized zirconia (YSZ) represents a typical example of such a material. The oxygen electrode is where the oxygen reduction reaction or the oxygen evolution reaction takes place according to the operation mode of the SOC. Lanthanum strontium manganite (LSM) has been the state-of-the-art oxygen electrode material for almost 25 years and is considered as a pure electron conductor. Lack of ionic conductivity of the LSM leads to limitation of the overall reaction rate to the amount of triple phase boundary (TPB) where gaseous phase, electron-conducting phase and ion-conducting are in simultaneous contact. According to the literature it is optimal for the electrode material to be mixed in the 50:50 ratio with YSZ to increase the amount of the TPB. Thus, the active zone is extended further from the electrolyte surface into the volume of the electrode body. Even though the mixed electrode material exhibits great performance, information on the optimal thickness of the electrode is scarce in the literature. The electrode thickness is a crucial parameter since not all of the electrode volume is electrochemically active and represents just surplus resistance for the electric current impairing the overall electrode performance. The goal of our research is to determine of the extent of the active zone that we can estimate the optimal thickness of the LSM—YSZ electrode for various operation conditions.A macrohomogenous 1D model was developed to simulate the active electrode zone extent. Initial parametric study has shown that the extent of the active region of the electrode is influenced by many factors including the kinetics of the occurring reactions, the ionic and electronic conductivity of the respective domains and working conditions, such as temperature and operating current density. Even though the literature offers data on the conductivity of bulk the LSM and YSZ, the data of the respective conductivities in the LSM—YSZ are not applicable due to the electrode structure. The conductivity of the structure consisting of packed particles with a small contact area is limited by the contact resistance. This study targets to determine the electronic conductivity of the LSM phase and the ionic conductivity of the YSZ phase in the LSM—YSZ electrode framework.The LSM conductivity in the electrode framework was determined by resistance measurement of the casted layers of the LSM—YSZ using electrochemical impedance spectroscopy (EIS). The results show an exponential decrease of the LSM conductivity with decreasing LSM content. Furthermore, the 50:50 LSM—YSZ exhibits conductivity comparable to that of the bulk YSZ electrolyte. This result proves that the energy losses due to the electrical resistance of the LSM—YSZ electrode cannot be neglected in the terms of SOC performance.The determination of the ionic conductivity of YSZ in the electrode framework required the substitution of LSM with an inert material. The material of choice was CaSO4 due to its availability and its melting point being relatively close to that of the LSM. Similarly to the LSM, YSZ exhibited an exponential decrease of ionic conductivity with a decrease in YSZ volume fraction in the samples. Furthermore, the trend was compared to the Koh-Fortini relationship, showing that grain boundaries have a strong influence on the total conductivity of the material.The results of the experiments helped us to determine the extent of the active electrode zone leading to the estimation of optimal thickness of the LSM—YSZ oxygen electrode thickness.The authors acknowledge the financial support of the Czech Science Foundation (GACR), contract No: 19-142-44-J and by the Technology Agency of the Czech Republic under project no. TK04030143.

Carbon nanotube logic gates: An interplay of spin and light

Carbon nanotubes (CNTs) are known to be the future of modern electronic devices due to their unique structure and extraordinary properties. In this paper, we modeled a first of its kind combinational carbon nanotube device consisting of a lanthanum strontium manganite molecule fused near the left CNT electrode and four-atom boron–nitrogen dopant atoms substituted near the right CNT electrode. Spin-resolved transport properties are studied using density functional theory. It is observed from the results that spin-resolved transport properties highly depend on the type of magnetic field applied and light conditions. The device shows efficient switching pattern and high spin filtration. The observations are made by calculating I–V characteristics, spin dependent transmission spectra, and molecular projected self-consistent Hamiltonian orbitals. Using light and spin polarization dependent properties, we have designed and realized the logic operations of and, or, and not gates. The study is useful to design a number of futuristic spin and light controlled electronic devices such as transistors, amplifiers, and oscillators.

Mechanochemical Synthesis of Soft Ferromagnetic Perovskite Lanthanum Strontium Manganite (La0.6Sr0.4MnO3)

Nanocrystalline La0.6Sr0.4MnO3 sample with perovskite structure was successfully prepared by mechanochemical synthesis. Mechanical treatment for 10 h followed by annealing at 1100 °C results in the formation of single perovskite lanthanum strontium manganite (LSMO) phase with rhombohedral crystal structure and symmetry. The heat-treated sample crystallite size, calculated from X-ray diffraction pattern, was about 84 nm. The scanning electron microscope images indicated a high degree of fine structure. The formation of single perovskite phase was confirmed by FTIR measurements. The magnetic measurements showed the soft ferromagnetic behavior of the obtained sample. The saturation magnetization was found to be lower than that expected from theoretical calculation for perfect ferromagnetic ordering and lower than the saturation magnetization published for bulk sample. This was explained in the light of the core/shell model of manganite nanoparticles. The obtained sample was found to have a negative coefficient of magnetoresistance at room temperature of about (−3.5%) with the application of 25 kOe magnetic field.

Smart Bone Graft Composite for Cancer Therapy Using Magnetic Hyperthermia

Magnetic hyperthermia (MHT) is a therapy that uses the heat generated by a magnetic material for cancer treatment. Magnetite nanoparticles are the most used materials in MHT. However, magnetite has a high Curie temperature (Tc~580 °C), and its use may generate local superheating. To overcome this problem, strontium-doped lanthanum manganite could replace magnetite because it shows a Tc near the ideal range (42–45 °C). In this study, we developed a smart composite formed by an F18 bioactive glass matrix with different amounts of Lanthanum-Strontium Manganite (LSM) powder (5, 10, 20, and 30 wt.% LSM). The effect of LSM addition was analyzed in terms of sinterability, magnetic properties, heating ability under a magnetic field, and in vitro bioactivity. The saturation magnetization (Ms) and remanent magnetization (Mr) increased by the LSM content, the confinement of LSM particles within the bioactive glass matrix also caused an increase in Tc. Calorimetry evaluation revealed a temperature increase from 5 °C (composition LSM5) to 15 °C (LSM30). The specific absorption rates were also calculated. Bioactivity measurements demonstrated HCA formation on the surface of all the composites in up to 15 days. The best material reached 40 °C, demonstrating the proof of concept sought in this research. Therefore, these composites have great potential for bone cancer therapy and should be further explored.

Oxygen nonstoichiometry and magnetic properties of doped manganites La0.7Sr0.3Mn0.95Fe0.05O3-δ

In this work, solid solutions of La0.7Sr0.3Mn0.95Fe0.05O3-δ with different oxygen content were obtained by the solid-phase reactions technique. Based on the investigation of the dynamics of changes in the oxygen index (3 – δ) during heating of the samples, the formation of a stressed state in their grains as a result of annealing was established. This results in a decrease in the mobility of oxygen vacancies during the reduction of cations according to the Mn4+ + e– → Mn3+ scheme and explains the decrease of released oxygen amount with an increase of δ as well as the heating rate of the samples. When studying the magnetic properties of the obtained samples, it was found that the temperature dependence of the magnetization obeys the Curie–Weiss law and as the oxygen defficiency increases, the Curie temperature for solid solutions decreases. It was found that the particles are in a frozen ferromagnetic state when measured in the low-temperature region of the М(Т) dependence in “zero-field mode” at Т ˂ ТВ. The presence of ferromagnetism at Т ˃ ТВ leads to a magnetically ordered state, in which the resulting magnetic moment of the magnetic particle is influenced by thermal fluctuations. When considering the temperature values of the magnetization of lanthanum-strontium manganite samples, it was found that with an increase of temperature in the low-temperature region, magnetic ordering is disturbed due to the excitation of magnons with a quadratic dependence of the energy from the wave vector, the number of which increases in proportion to T3/2. This results in a decrease in the manganite magnetization. The observed temperature dependence of the magnetization measured in the “field-cooling mode” was approximated taking into account the quadratic and non-quadratic dispersion laws of the magnon spectrum.

Generalized Poisson-Nernst-Planck-Based Physical Model of the O2∣LSM∣YSZ Electrode

The paper presents a generalized Poisson-Nernst-Planck model of an yttria-stabilized zirconia electrolyte developed from first principles of nonequilibrium thermodynamics which allows for spatial resolution of the space charge layer. It takes into account limitations in oxide ion concentrations due to the limited availability of oxygen vacancies. The electrolyte model is coupled with a reaction kinetic model describing the triple phase boundary with electron conducting lanthanum strontium manganite and gaseous phase oxygen. By comparing the outcome of numerical simulations based on different formulations of the kinetic Eqs. with the results of EIS and CV measurements we attempt to discern the existence of separate surface lattice sites for oxygen adatoms and surface oxides from the assumption of shared ones. Moreover, we show that the mass-action kinetics model is sensitive to oxygen partial pressure unlike exponential kinetics models. The resulting model is fitted to a dataset of EIS and CVs spanning multiple temperatures and pressures, using various relative weights of EIS and CV data in the fitness function. The model successfully describes the physics of the interface around the OCV.

Current trends in the description of lanthanum strontium manganite oxygen electrode reaction mechanism in a high-temperature solid oxide cell

This review summarizes recent progress in understanding the oxygen reduction and evolution reactions at the lanthanum strontium manganite electrode of a high-temperature solid oxide cell. Information provided here is put into the perspective of the defect chemistry of lanthanum strontium manganite and its impact on the electrode reaction mechanisms itself. After summarizing recent views on the oxygen reduction reaction mechanism, the focus turns to the oxygen evolution reaction, which is significantly less treated in the literature. A combination of the information in the literature on both reactions was the basis for modified reaction mechanism of the oxygen evolution reaction to be proposed under consideration of recent experimental observations and theoretical findings. • Oxygen evolution and reduction reactions mechanism in solid oxide cells analysed. • LSM defect chemistry considered in the reaction mechanism discussion. • LSM electrode polarisation history role introduced. • Modification of LSM electrode state may result in reaction mechanism alternation. • Switching between two and three phase boundary mechanism considered.

Investigating the effect of nano-structured magnetic particles lanthanum strontium manganite on perovskite solar cells

In this study, pure phase nanostructured strontium-doped lanthanum manganite, La0.75Sr0.25MnO3 (LSM), with a hexagonal structure was synthesized by sonochemical method. Then, XRD and SEM estimated the size of the LSM nanopowders. The results are exhibited that products synthesized in this method are compatible with particle size and morphology. Magnetic measurement was done by vibrating sample measurement (VSM) on LSM nanoparticles at room temperature. According to the results obtained from VSM displayed the saturation magnetization of LSM nanoparticles exhibited a maximum of 24.25 emu/g at room temperature. Then, the influence of LSM nanoparticle as an additive on the film morphology of CH3NH3PbI3 and the performance of perovskite solar cells was examined. We explore by using 5wt % of additive can increase the short current density (Jsc) from 14.45±0.55 to 18.29±0.38 mA/cm2 (~ 26.5 % enhancement) and power-conversion efficiency (PCE) from 8.33±0.40 to 12.41±0.35 (~ 49 % enhancement). Moreover, the morphology, and band gap of the new perovskite layer was improved.