LaNiO3 Research Articles

Enhanced Grain Boundary Resistance Resulting in High Permittivity and Low Dielectric Loss in CaCu3Ti4O12/LaNiO3

(1-X) CaCu3Ti4O12 + (X) LaNiO3 composite ceramics were fabricated using pre-reacted calcium copper titanate CaCu3Ti4O12 (CCTO) and lanthanum nickelate LaNiO3 (LNO) and their crystallographic structure and morphology were studied to measure dielectric, impedance, and conductivity values. X-ray diffraction peaks show that CCTO/LNO composites are in a cubic structure. Scanning electron microscopy images show denser and more uniform grains with thin grain boundaries and a smaller average grain size. The permittivity of CCTO is stable in the range 102–106 Hz, but the composites show huge progress in permittivity by space charge polarization and relaxation in the range 103–104 Hz, demonstrating improved dielectric properties. The 0.98(CaCu3Ti4O12)+0.02(LaNiO3) sample showed a dielectric constant of 2.58 × 104 at 1 kHz, which is superior to pure CCTO (2.28 × 104 at 1 kHz). The electrical behaviour of the metallic filler on the composites was investigated using impedance spectroscopy analysis. The resistance of grain boundary increases with LNO. Activation energies were found to be 0.92, 0.95, and 0.90 eV for x = 0.1, 0.2, and 0.3, respectively, and these values are better than that of pristine CCTO (0.85 eV) sample. These results indicate that the prepared CCTO/LNO samples could be useul for high energy applications.

Regenerable Ni-Au/La2O3 catalysts for dry reforming of methane

Dry reforming of methane (DRM) has been proposed as an effective way of converting CO2 and CH4, two major greenhouse gases, into synthesis gas (H2 + CO), a ubiquitous feedstock for various chemical industries. Ni-based bimetallic catalysts have been widely explored as an attractive route to improve DRM activity, selectivity, and stability. In this study, we synthesized LaNiO3 (LNO) and 1% Au-doped LaNiO3 (Au/LaNiO3 – A/LNO) using the modified sol-gel method. The material properties were studied using various characterization techniques, including XRD, BET, H2-TPR, TPO, STEM-HAADF with EDX mapping, Raman spectroscopy, and XPS. Ni nanoparticles with sizes ranging from 10 to 70 nm were successfully exsolved from the perovskite material after reduction at 800 °C. DRM activity of the reduced catalysts was probed from 400 to 800 °C. The Au-doped LNO exhibits significant enhancement in DRM activity at a lower temperature range (600–700 °C) compared to LNO. The A/LNO was also shown to retard coke formation and improve the selectivity for DRM. A computational study using density functional theory (DFT) reveals that the Ni3Au sites have a lower methane activation barrier due to the formation of NiAu alloy and the synergetic effect between Ni and Au.

Structural and physical properties of Pb(Zr0.4Ti0.6)O3 epitaxial film with LaNiO3 electrodes

Epitaxial LaNiO3 (LNO)/PbZr0.4Ti0.6O3 (PZT)/LaNiO3 heterostructures have been deposited on LaAlO3 (LAO) substrates, in which LNO films were prepared by magnetron sputtering and PZT films with thicknesses ranging from 40 nm to 160 nm were deposited via sol-gel method. It is found that the structural and physical properties of PZT films are closely related to the tetragonality (c/a-1). With increasing PZT thickness, both tetragonality and remanent polarization increase, and the maximum tetragonality and remanent polarization correspond to a 120-nm-thick PZT film capacitor with a remanent polarization of 61.6 μC/cm2 measured at 425.00 kV/cm. However, as the thickness of PZT film is further increased, the ferroelectric polarization decreases which is attributed to relaxation of the PZT film. The leakage current mechanism of the capacitor remains unchanged regardless of the PZT thickness. It is Space Charge Limited Current (SCLC) conduction mechanism at high electric fields and Ohmic conduction mechanism at low electric fields.

Acid etching-induced nanocutting of LaNiO3 transplanting self-assembled photodiode array-like LaNiO3/N,P-RGO nanoreactor for efficient photocatalytic hydrogen evolution

Nanoscale graphene-semiconductor composite photocatalysts with fascinating properties in the photocatalytic hydrogen evolution have inspired numerous interests in broad research fields. The architectures with efficient light response and promoting charge separation at the interface between reduced graphene oxide (RGO) and semiconductor are critical, yet synthesizing them remains a formidable challenge. Herein, the photodiode array-like LaNiO3/N,P-RGO (LNO/N,P-RGO) nanoreactor was constructed using an innovative strategy of acid etching-induced nanocutting self-assembly. Ammonium dihydrogen phosphate working as both a nitrogen phosphorus co-dopant and an acid etching reagent, cuts perovskite LaNiO3 (LNO) nanoparticles into nanorods, which are bonded evenly on the nitrogen phosphorus co-doped reduced graphene oxide (N,P-RGO) to form an n-n semiconductor heterojunction LNO/N,P-RGO as a photodiode array-like nanoreactor via hydrothermal treatment. The photodiode array-like nanostructure exposes more active sites that are conducive to light absorption. The robust Ni-C and P-O bonds promote the narrowing of space-charge region at the interface by UV irradiation, thereby improving the transport of photogenerated carriers by visible light irradiation. The LNO/N,P-RGO nanoreactor exhibits excellent photocatalytic hydrogen evolution performance with a yield of up to 354 μmol g−1 h−1 under UV–visible light, which is 50 times higher than that of pure perovskite LNO, and it also displays favorable recycling stability.

Investigation of electronic, ferroelectric and local electrical conduction behavior of RF sputtered BiFeO3 thin films

Most of the applied research on BiFeO3 (BFO) focuses on magnetoelectric and spintronic applications. This calls for a detailed grasp of multiferroic and conduction properties. BFO thin films with (100) epitaxial growth has been deposited on a LaNiO3 (LNO) buffered Pt/Ti/SiO2/Si(100) substrate using RF magnetron sputtering. The film formed at 15 mTorr, 570 °C, and with Ar/O2 4:1 had a reasonably high degree of (100)-preferential orientation, the least surface roughness, and a densely packed structure. We obtained ferroelectric loops with strong polarization (150 μC cm−2). The leakage current density is as low as 10–2 A cm−2 at 100 kV cm−1, implying that space-charge-limited bulk conduction (SCLC) was the primary conduction channel for carriers within BFO films. Local electrical conduction behavior demonstrates that at lower voltages, the grain boundary dominates electrical conduction and is linked to the displacement of oxygen vacancies in the grain boundary under external electric fields. We hope that a deeper understanding of the conduction mechanism will help integrate BFO into viable technologies.

Improved electrical properties in PZT/PZ thin films by adjusting annealing temperature

In this study, PbZr0.52Ti0.48O3/PbZrO3 (PZT/PZ) multilayer films were prepared on SiO2/Si substrate buffered with LaNiO3 (LNO) thin films, and then annealed at different temperatures by rapid thermal annealing (RTA) technology. The phase structures, microstructures, and electrical properties of the obtained PZT/PZ multilayer films were studied. According to the results of XRD and SEM, it was found that the PZ films with perovskite phase were obtained by annealing at 650 °C firstly. The PZT films on crystallized PZ films were in amorphous phase after annealing at 450 °C, in pyrochlore phase after annealing at 550 °C, and finally in perovskite phase at annealing temperature higher than 600 °C. The multilayer films with the PZT films annealed at 550 °C exhibited linear hysteresis loops, and such films showed the enhanced energy storage density of 31.6 J cm−3 and the energy storage efficiency of 66.9% at a high breakdown field strength of 2475 kV cm−1. The experimental results proved that the phase structure of the PZT/PZ multilayer films can be regulated by different annealing temperatures, which could further enhance the energy storage performance of the PZT/PZ multilayer films.

Synergistic Effects in LaNiO3 Perovskites between Nickel and Iron Heterostructures for Improving Durability in Oxygen Evolution Reaction for AEMWE.

Perovskite materials that aren't stable during the oxygen evolution reaction (OER) are unsuitable for anion-exchange membrane water electrolyzers (AEMWE). But through manipulating their electronic structures, their performance can further increase. Among the first-row transition metals, nickel and iron are widely recognized as prominent electrocatalysts; thus, the researchers are looking into how combining them can improve the OER. Recent research has actively explored the design and study of heterostructures in this field, showcasing the dynamic exploration of innovative catalyst configurations. In this study, a heterostructure is used to manipulate the electronic structure of LaNiO3 (LNO) to improve both OER properties and durability. Through adsorbing iron onto the LNO (LNO@Fe) as γ iron oxyhydroxide (γ-FeOOH), the binding energy of nickel in the LNO exhibited negative shifts, inferring nickel movement toward the metallic state. Consequently, the electrochemical properties of LNO@Fe are further improved. LNO@Fe showed excellent performance (1.98Acm-2, 1m KOH, 50°C at 1.85V) with 84.1% cell efficiency in AEMWE single cells, demonstrating great improvement relative to LNO. The degradation for the 850h durability analysis of LNO@Fe is ≈68mVkh-1, which is ≈58 times less than that of LNO.

An experimental and theoretical approach for the biogas dry reforming reaction using perovskite-derived La0.8X0.2NiO3-δ catalysts (X = Sm, Pr, Ce)

The work presented herein reports on the investigation of the biogas dry reforming catalytic performance of LaNiO3 (LNO), La0.8Sm0.2NiO3 (LSNO), La0.8Pr0.2NiO3 (LPNO) and La0.8Ce0.2NiO3 (LCNO). The perovskite-type materials were synthesized via citrate sol-gel and characterized using XRD, N2 physisorption H2-TPR, H2-TPD, TEM, HAADF-STEM and XPS. The performance of all catalysts in terms of both activity and stability was examined in order to assess the effect of temperature on the CH4 and CO2 conversion, as well as on the H2 and CO yield and the H2/CO molar ratio of the produced gas mixture. Experimental results showed that modification of LaNiO3 with Sm and Pr enhanced the catalytic performance in terms of catalytic stability and reduced the order/crystallinity of the deposited coke. A theoretical model was also produced in Python with the purpose of simulating the catalytic performance. Modelling results showed a good agreement with the experimental values and therefore confirm the validity of the model for predicting the dry reforming catalytic performance.

Charge-Transfer-Induced Interfacial Ferromagnetism in Ferromagnet-Free Oxide Heterostructures.

Due to the strong interlayer coupling between multiple degrees of freedom, oxide heterostructures have demonstrated exotic properties that are not shown by their bulk counterparts. One of the most interesting properties is ferromagnetism at the interface formed between "nonferromagnetic" compounds. Here we report on the interfacial ferromagnetic phase induced in the superlattices consisting of the two paramagnetic oxides CaRuO3 (CRO) and LaNiO3 (LNO). By varying the sublayer thickness in the superlattice period, we demonstrate that the ferromagnetic order has been established in both CaRuO3 and LaNiO3 sublayers, exhibiting an identical Curie temperature of ∼75 K. The X-ray absorption spectra suggest a strong charge transfer from Ru to Ni at the interface, triggering superexchange interactions between Ru/Ni ions and giving rise to the emergent ferromagnetic phase. Moreover, the X-ray linear dichroism spectra reveal the preferential occupancy of the d3z2-r2 orbital for the Ru ions and the dx2-y2 orbital for the Ni ions in the heterostructure. This leads to different magnetic anisotropy of the superlattices when they are dominated by CRO or LNO sublayers. This work clearly demonstrates a charge-transfer-induced interfacial ferromagnetic phase in the whole ferromagnet-free oxide heterostructures, offering a feasible way to tailor oxide materials for desired functionalities.

Layered Ferromagnetic Structure Caused by the Proximity Effect and Interlayer Charge Transfer for LaNiO3/LaMnO3 Superlattices.

Magnetic proximity-induced magnetism in paramagnetic LaNiO3 (LNO) has spurred intensive investigations in the past decade. However, no consensus has been reached so far regarding the magnetic order in LNO layers in relevant heterostructures. This paper reports a layered ferromagnetic structure for the (111)-oriented LNO/LaMnO3 (LMO) superlattices. It is found that each period of the superlattice consisted of an insulating LNO-interfacial phase (five unit cells in thickness, ∼1.1 nm), a metallic LNO-inner phase, a poorly conductive LMO-interfacial phase (three unit cells in thickness, ∼0.7 nm), and an insulating LMO-inner phase. All four of these phases are ferromagnetic, showing different magnetizations. The Mn-to-Ni interlayer charge transfer is responsible for the emergence of a layered magnetic structure, which may cause magnetic interaction across the LNO/LMO interface and double exchange within the LMO-interfacial layer. This work indicates that the proximity effect is an effective means of manipulating the magnetic state and associated properties of complex oxides.

Growth of p/n-type BiFeO3 thin films for construction of a bilayer p–n junction for photodegradation of organic pollutants

BiFeO3 (BFO) films were grown on LaNiO3 (LNO) buffered glass substrates under tailored conditions to exhibit either n-type or p-type conductivity, allowing fabrication of a bilayer p–n junction for efficient photodegradation of organic pollutants.

Interplay Between Electron Correlations, Magnetic State, and Structural Confinement in LaNiO<sub>3</sub> Ultrathin Films

We report a theoretical study of the effects of electron correlations and structural confinement on the electronic properties and magnetic state of LaNiO3(LNO) thin films epitaxially deposited on the(001)LaAlO3(LAO) substrate. Using the DFT + U method we compute the electronic band structure, magnetic properties, and phase stability of the 1.5 unit-cell-thick NiO2-terminated LNO thin films. Our results reveal complex diversity of the electronic states caused by the effects of structural confinement, interfacial charge transfer and electronic correlations. Our calculations suggest the appearance of in-plane (110) charge disproportionation of the Ni ions in the interface NiO2layer of the antiferromagnetically ordered LNO thin films. Moreover, the electronic states of both the antiferromagnetic and ferromagnetic LNO/LAO show a large orbital polarization of the Ni ions in the surface NiO2layers. Our results suggest the crucial importance of oxygen defects to explain the metal-to-insulator phase transition experimentally observed in a few-unit-cell-thick LNO/LAO thin films.

Insights into the ferromagnetism-antiferromagnetism transition: A first-principles study of LaFexNi1-xO3 (0≤x≤0.5)

The effect of different Fe doping concentration (x = 0.125, 0.25, 0.375 and 0.5) on electronic structure and magnetic properties of LaNiO3 (LNO) have been performed on the spin polarization calculations based on first principles. The calculation results show that with the increase of Fe dopant concentration, LaFexNi1-xO3 undergoes a magnetic transition from ferromagnetism (FM) to antiferromagnetism (AFM). The net magnetic moments of LaFe0.125Ni0.875O3, LaFe0.25Ni0.75O3, LaFe0.375Ni0.625O3 and LaFe0.5Ni0.5O3 in the FM ground state are found to be 12.00 µB/supercell, 16.00 µB/supercell, 20.06 µB/supercell and 23.96 µB/supercell, respectively. In the magnetic configuration of AFM of LaFexNi1-xO3 (x = 0.125 and 0.375) with the nearest doping position, the asymmetric magnetic structure leads to the symmetry of the spin-ordered AFM network is broken, resulting in the generation of net magnetic moment of -3.06 µB and 3.87 µB. The net magnetic moment in LaFexNi1-xO3 mainly originates from transition metals (TM) Fe, Ni and magnetized O atoms.

Optimization of a LaNiO3 Bottom Electrode for Flexible Pb(Zr,Ti)O3 Film-Based Ferroelectric Random Access Memory Applications

The direct growth of ferroelectric films onto flexible substrates has garnered significant interest in the advancement of portable and wearable electronic devices. However, the search for an optimized bottom electrode that can provide a large and stable remnant polarization is still ongoing. In this study, we report the optimization of an oxide-based LaNiO3 (LNO) electrode for high-quality Pb(Zr0.52Ti0.48)O3 (PZT) thick films. The surface morphology and electrical conductivity of sol-gel-grown LNO films on a fluorophlogopite mica (F-mica) substrate were optimized at a crystallization temperature of 800 °C and a film thickness of 120 nm. Our approach represents the promising potential pairing between PZT and LNO electrodes. While LNO-coated F-mica maintains stable electrical conductivity during 1.0%-strain and 104-bending cycles, the upper PZT films exhibit a nearly square-like polarization–electric field behavior under those stress conditions. After 104 cycles at 0.5% strain, the remnant polarization shows decreases as small as ~14%. Under flat (bent) conditions, the value decreases to just 81% (49%) after 1010 fatigue cycles and to 96% (85%) after 105 s of a retention test, respectively.

Application of samarium doped lanthanum nickel oxide perovskite nanocatalyst for biodiesel production

The catalytic performance of the synthesized LaNiO3 (LNO) and LaSmNiO3 (L1-xSxNO) perovskite structures as novel efficient catalysts for the conversion of waste cooking oil (WCO) to biodiesel was evaluated. The synthesized heterogeneous catalysts of LNO and L1-xSxNO were characterized via Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), Brunauer, Emmett, and Teller (BET), inductively coupled plasma-optical emission spectrometer (ICP-OES), and Power X-ray diffraction (XRD). The crystal size of LNO was obtained to be around 31 nm at 2θ of 47.31° using Scherrer's equation. Catalysts characterization revealed that doping Sm with LNO (L0.9S0.1NO) enhanced the surface area from 7.71 to 15.75 m2/g, and thus may provide more active sites for transesterification reaction. Also, the Sm doping causes numerous oxygen vacancies in the structure of perovskite, improving the catalyst's ability to catalyze reactions. To determine the optimum conditions in the WCO transesterification process, the response surface methodology (RSM) based central composite design (CCD) was applied. The influences of key parameters including MeOH/WCO ratio (5–20 mol/mol), reaction duration (1–5 h), catalyst mass fraction (1–5 wt%), and reaction temperature (60–120 °C) were explored on the behavior of the reaction. It is inferred that the L0.9S0.1NO catalyst has excellent catalytic activity in converting WCO to biodiesel. The experimental and modeling sensitivity analysis indicated that the application of L0.9S0.1NO catalyst led to the WCO conversion of 95.14 % to biodiesel at MeOH/WCO ratio of 9.07, reaction duration of 3.02 h, catalyst mass fraction of 3.08 wt%, and reaction temperature of 80.07 °C.

First-principles study on the magnetic properties in non-metallic co-doped cubic LaNiO3

Using the first principles spin polarized calculations, the electronic structures and magnetic properties of two C atoms and two S atoms doped LaNiO3 (LNO) are investigated. For the double C-doped LNO (C-LNO), C–O–C chain exhibits the ferromagnetic (FM) order arrangement. The introduction of C atoms increases the average magnetic moment of each Ni atom by 0.23 μB/cell and enhances the hybridization between Ni-3d and O-2p states. The C atom generates a weak magnetic moment of 0.07 μB/atom due to the magnetization in the FM ground state. For the case of double S-doped LNO (S-LNO), S–O–S chain exhibits the antiferromagnetic (AFM) order. In the ferromagnetic configuration of S-LNO, each S atom generates a magnetic moment of 0.18 μB/atom due to the Ni–O hybridization. In addition, the interesting phenomenon of magnetic moment reversal of S atoms is observed in both the FM and AFM structures of S-LNO.

Reset-First and Multibit-Level Resistive-Switching Behavior of Lanthanum Nickel Oxide (LaNiO3-x) Thin Films.

The resistive random-access memory (RRAM) with multi-level storage capability has been considered one of the most promising emerging devices to mimic synaptic behavior and accelerate analog computations. In this study, we investigated the reset-first bipolar resistive switching (RS) and multi-level characteristics of a LaNiO3-x thin film deposited using a reactive magnetron co-sputtering method. Polycrystalline phases of LaNiO3 (LNO), without La2O3 and NiO phases, were observed at similar fractions of Ni and La at a constant partial pressure of oxygen. The relative chemical proportions of Ni3+ and Ni2+ ions in LaNiO3-x indicated that it was an oxygen-deficient LaNiO3-x thin film, exhibiting RS behavior, compared to LNO without Ni2+ ions. The TiN/LaNiO3-x/Pt devices exhibited gradual resistance changes under various DC/AC voltage sweeps and consecutive pulse modes. The nonlinearity values of the conductance, measured via constant-pulse programming, were 0.15 for potentiation and 0.35 for depression, indicating the potential of the as-fabricated devices as analog computing devices. The LaNiO3-x-based device could reach multi-level states without an electroforming step and is a promising candidate for state-of-the-art RS memory and synaptic devices for neuromorphic computing.

Effect of sputtering-target composition on the structure, dielectric, ferroelectric, and energy storage properties of highly (00l)-oriented Ba(ZrxTi1–x)O3 films

It is relatively easy to obtain highly oriented/textured Ba(ZrxTi1–x)O3 (BZT) films by magnetron sputtering, but it is complicated to control the composition of these sputtered oriented films. Here, a series of BZT ceramic targets with different ingredients (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) and a BaTiO3 (x = 0) target were fabricated by solid-state sintering. Then, the corresponding BZT thin films were deposited on LaNiO3 (LNO) buffered Pt/Ti/(001)Si substrates adopting radio-frequency magnetron sputtering. Benefit from the prefabricated (001)-LNO buffer layer and optimized BZT film preparation process, all BZT films exhibit highly (00l) preferred orientation. However, the degree of orientation, lattice parameter, dielectric properties, ferroelectric behaviors, and energy-storage characteristics are all highly dependent on the Zr content of BZT films sputtered by targets with the same composition. (00l)-oriented BZT films with relatively low Zr content have a better crystalline structure [narrower full width at half maximum (FWHM), larger grains]. It is also found that the rising of the Zr content in (00l)-oriented BZT films will result in a larger out-of-plane lattice parameter, and these results indicate that the doping amount of Zr will strongly change the heterointerface stress/strain states and the growth mode of the oriented films, and then effectively tailor their electric performances.

Controllable resistive switching behaviors in heteroepitaxial LaNiO3/Nb:SrTiO3 Schottky junctions through oxygen vacancies engineering

Perovskite oxide-based memristors have been extensively investigated for the application of non-volatile memories, and the oxygen vacancies associated with Schottky barrier changing are considered as the origin of the memristive behaviors. However, due to the difference of device fabrication progress, various resistive switching (RS) behaviors have been observed even in one device, deteriorating the stability and reproducibility of devices. Precisely controlling the oxygen vacancies distribution and shedding light on the behind physic mechanism of these RS behaviors, are highly desired to help improve the performance and stability of such Schottky junction-based memristors. In this work, the epitaxial LaNiO3 (LNO)/Nb:SrTiO3 (NSTO) is adopted to explore the influence of oxygen vacancy profiles on these abundant RS phenomena. It demonstrates that the migration of oxygen vacancy in LNO films plays a key role in memristive behaviors. When the effect of oxygen vacancies at the LNO/NSTO interface is negligible, improving the oxygen vacancies concentration in LNO film could facilitate resistance on/off ratio of HRS and LRS, and the corresponding conducting mechanisms attributes to the thermionic emission and tunneling-assisted thermionic emission, respectively. Moreover, it is found that reasonably increasing the oxygen vacancies at LNO/NSTO interface makes trap-assisted tunneling possible, also providing an effective way to improve the performance of the device. The results in this work have clearly elucidated the relationship between oxygen vacancy profile and RS behaviors, and give physical insights into the strategies for improving the device performance of Schottky junction-based memristors.

Boosted Photocurrent via Heating BiFeo3 Thin Film for UV Photodetector at Wide Temperature Range

AbstractThe current research on ferroelectric photovoltaic materials is concentrated on enhancing the output photocurrent. As solar cells operate at high temperatures, it is crucial to take into account the effect of increasing temperatures on ferroelectric photovoltaics. In this study, an LNO (lanthanum nickelate, LaNiO3)/BFO (bismuth ferrate, BiFeO3)/ITO (indium tin oxide) device is constructed on a mica substrate by sol–gel method. The device achieves output photocurrent enhancement at a wide temperature range (33–183 °C), with the largest photocurrent enhancement at 130 °C, which is 178% relative to room temperature, and the output power is also increased by 9.88 times. At the same time, compared with BFO bulk, it is found that the performance of BFO film is always higher than that of bulk in the test temperature range, and the output photocurrent of BFO film at room temperature is 104 times higher than that of bulk. This article investigates the effect of high temperatures on ferroelectric photovoltaics and also provides a strategy for enhancing the photovoltaic performance of ferroelectric films, providing guidance for future applications of ferroelectric films in flexible solar cells and other applications.