Europium Titanate Research Articles

Refrigeration capacity modeling of europium titanate based magnetocaloric compounds using computational single hidden layer intelligent and random forest regression methods

Europium titanate (EuTiO3) is a quantum para-electric magnetocaloric compound with potential application in green magnetic cooling technology. Super-exchange and indirect interactions existing between the magnetic moments of this compound are responsible for the observed magnetic properties such as the refrigeration capacity which falls among the key factors that characterize the usefulness of magnetic system of cooling in addressing energy crisis. Crystallographic substitutions and ionic replacement potentially shift magnetic ordering between anti-ferromagnetism to ferromagnetism and ultimately alters the refrigeration (magnetic) capacity of EuTiO3 compound. This work proposes extreme learning machine (ELM) and random forest regression (RFR) computational approaches to model refrigeration capacity of europium titanate magnetic refrigerant with the aid of applied magnetic field, ionic concentrations and ionic radii predictors. Sigmoid activation based extreme learning machine algorithm(SGA-ELM) demonstrates superior performance over sine function activation based extreme learning machine algorithm(SIA-ELM) with improvement of 0.03 %, 16.04 % and 35.03 % on the basis of Pearson correlation coefficient (CC), root mean square error (RMSE) and mean absolute error (MAE) performance yardsticks, respectively on testing set of EuTiO3 based magnetocaloric compounds. SGA-ELM performs better than SIA-ELM and RFR model with improvement of 35.03 % and 66.84 %, respectively while SIA-ELM model performs better than RFR model with improvement of 59.97 %. SGA-ELM model developed in this work outperforms the existing swarm based support vector regression (SW-SVR) models with performance improvement of 15.38 % (for SW-SVR-Gas with Gaussian function) and 42. 71 % % (for SW-SVR-Pol with polynomial function) using mean absolute deviation (MAD) performance yardstick. Significance of magnetic field and dopants concentrations on refrigeration capacity of different EuTiO3 perovskite was investigated with SGA-ELM model. The accuracy of developed models in determining refrigeration capacity of EuTiO3 compounds would ultimately circumvents experimental challenges and explores future potentials of these classes of compound for addressing present and future energy crisis in cooling industries.

A Route for Fabricating Epitaxial Europium Titanate Film in a Wide Strain Range

A Route for Fabricating Epitaxial Europium Titanate Film in a Wide Strain Range

Synthesis and Characterization of the Electrical and Energy Storage Properties of New Barium Titanate - Europium Titanate Solid Solution

In the present work, the investigation of the structural, dielectric, ferroelectric and energy storage properties of polycrystalline samples of (1-x)BaTiO3 – xEuTiO3 (BT-ET) solid solution materials prepared by conventional solid-state reaction method has been carried out. X-ray diffraction analyses have revealed the formation of a single-phase tetragonal structure with the P4mm space group. Furthermore, the temperature dependence of the dielectric constants marked the presence of the following sequence of structural phase transitions, namely from rhombohedral to orthorhombic, from orthorhombic to tetragonal and from tetragonal to cubic phase transitions with the increase of temperature. A diffuse phase transition has been observed from the dielectric permittivity peak and has been analyzed using the modified Curie-Weiss law and the degree of diffuseness is found to be in the range of 1.16 - 1.76 due to the existence of different states of polarization. A phase diagram has been established based on the temperature-dependent dielectric permittivity studies. The room temperature ferroelectric properties point to a coercive field larger than that of BaTiO3 ceramics. Broad dielectric peaks associated with diffuse phase transition appear in a wide temperature range (40 - 100 °C) with the highest dielectric permittivity ε’ = 6498 found in the x = 0.05 ceramics. Moreover, an improved energy storage performance is obtained in the 0.95BaTiO3-0.05EuTiO3 ceramic with a recoverable energy density of Wrec = 0.797 J/cm3, coupled with an efficiency η = 73% at 170 kV/cm and the highest storage energy density of Wst = 1.571 J/cm3 is obtained for 0.90BaTiO3-0.10EuTiO3, which is superior to other lead-free BT-based ceramics. All these features demonstrate that the BT-ET ceramics can be widely used in energy storage applications and also in high-temperature multilayer capacitors for automotive, aerospace and related industries.

Modeling magnetic refrigeration capacity of doped EuTiO3 magnetocaloric compounds using swarm based intelligent computational method

This work models the magnetic refrigeration capacity (MRC) of doped europium titanate (EuTiO3) at different applied magnetic field using hybrid particle swarm optimization based support vector regression (SW-SVR) algorithm with ionic radii dopant descriptors. The developed model with Gaussian function (SW-SVR-Gas) shows better performance as compared with polynomial based model (SW-SVR-Pol) with improvement of 35.76 %, 0.13 % and 45.76 % using mean absolute error (MAE), correlation coefficient (CC) and root mean square error (RMSE) performance yardsticks, respectively. The developed SW-SVR-Gas model investigates the behavior of Eu1-xBaxTiO3 and EuTi1-xNixO3 doped europium titanate at different dopants concentration as well as applied field. Novelties of the developed model include circumvention of experimental difficulties associated with magnetic refrigeration capacity determination, implementation of simple molecular descriptors with high precision and accuracy. The demonstrated uniqueness of the developed model would strengthen exploration of refrigeration capacity of europium titanate based compounds for addressing global refrigeration crisis.

Sol‐gel route to nanocrystalline Eu2Ti2O7 films with tailored structural and optical properties

AbstractWe present a generic sol‐gel approach for the preparation of highly transparent europium titanate Eu2Ti2O7 films with tailored structural and optical properties. The films were prepared by a sol‐gel process and thermally treated in a rapid thermal annealing furnace. We determined the effects of the annealing temperature on structural, morphological, and optical properties of the films. We evaluated film's optical constants. The size of the primary nanocrystals and the film's refractive index were tailored by the annealing temperature. The crystallization of Eu2Ti2O7 started at 800°C and the nanocrystals grew with increasing annealing temperature reaching the size from 20 nm to 100 nm. The energy of nanocrystal growth was 21 ± 3 kJ·mol−1. Increasing nanocrystal size caused the regular growth of the refractive index recorded at 632 nm from 2.07 to 2.17 for the films annealed at 800°C and 1200°C, respectively. These results provide fundamental information about the effects of the structure and the morphology of the films on their optical properties. The presented approach can be extended to other rare earth‐doped titanates and these films can be used as passive protective coatings as well as active materials suitable for photonic and spintronic applications.

Investigation of europium titanate EuTiO3 obtaining process by method of Eu2O3 and TiO2 solid-phase sintering in presence of carbon

Investigation of europium titanate EuTiO3 obtaining process by method of Eu2O3 and TiO2 solid-phase sintering in presence of carbon

Effect of structural and Eu3+ amount in TiO2 semiconductor material on downconversion photoluminescence properties

The search for new materials for application in energy production and conversion has identified inorganic oxides doped with rare earth ions as promising candidates for the construction of photovoltaic devices for energy conversion. This work presents the synthesis of TiO2 powders doped with Eu3+, using propylene glycol in the reaction medium, changing the europium percentage at 0.2, 3 and 7 mol%, and heat-treated at 700, 750, 800 and 900 °C for 8 h. The results of X-ray diffraction showed the formation of TiO2 polymorphs (anatase and rutile), both belonging to the tetragonal system and also the formation of europium titanate. The Rietveld refinement showed the deformation of the network parameters and volume of the unit cell, as well as the percent composition of the phases. Raman spectroscopy corroborated the results of XRD. Photoluminescence results showed that the synthesized materials have intense emission in the red region with the most intense band positioned at 614 nm assigned to the 5D0→7F2 transition of Eu3+ mainly in the sample with 3 mol% of Eu3+ heat-treated at 700 °C. The life time results showed that the photoluminescence of the materials are dependent on the crystalline structure, the host matrix in which the Eu3+ is localized, and the amount of the dopant in the sample. According to the results obtained in this work, the materials have the interesting downconversion effect, being a great absorber of UV–vis energy and converting that energy to the visible region. Materials with these photoluminescence properties associated with the structural properties are very interesting for use in the improvement of solar cells.

Synthesis, characterization, and morphological control of Eu2Ti2O7 nanoparticles through green method and its photocatalyst application

Nowadays, in connection with the increasing pollution of the environment, several studies are performed in order to find new group of compounds which could replace chemical synthesis capping agents due to their high toxicity to ecosystem and difficulty in being degraded in the environment. In the current study, an attempt is made to synthesize europium titanate (Eu2Ti2O7) nanoparticles through a green method with the aid of natural capping agents such as glucose, fructose, galactose, lactose and starch in an aqueous solution and investigate their effect on the morphology and particle size of final products. According to the vibrating sample magnetometer result, Eu2Ti2O7 nanoparticles indicated a paramagnetic behavior at room temperature. In addition, methyl orange was chosen as a dye water pollution to evaluate its degradation by as-synthesize Eu2Ti2O7 nanoparticles under ultraviolet light irradiation. Furthermore, the photocatalysis results reveal that the maximum decolorization of 94 % for methyl orange occurred with Eu2Ti2O7 nanoparticles in 60 min under ultraviolet light irradiation.

Luminescence properties of nanocrystalline europium titanate Eu2Ti2O7

Nanocrystalline europium titanate Eu2Ti2O7 with tailored structural properties was prepared by a sol–gel approach. Structural properties of prepared nanocrystals were correlated to the steady-state and time-resolved luminescence spectroscopy of europium ions incorporated within formed nanocrystals. The formation of nanocrystalline Eu2Ti2O7 raised up the existence of two inequivalent positions of Eu3+ ions. Eu3+ ions displaced in highly symmetrical positions within the pyrochlore lattice provided low intensity luminescence and lifetime shorter than 10μs. Eu3+ ions displaced in asymmetrical positions on the surface of formed nanoparticles provided lifetimes on the level of 50μs. Number of Eu3+ ions displaced in asymmetrical positions was decreased according to increase size and crystallinity of formed nanocrystals. The presented results provide fundamental information about the influence of the structure and the morphology of formed nanocrystals to their luminescence properties.

Enthalpy increment measurements on europium titanate

Europium titanate is a potential control rod material. Enthalpy increments of europium titanate (Eu2TiO5) were measured in the temperature range 770–1,747 K by employing the method of inverse drop calorimetry using a high-temperature differential calorimeter. Thermodynamic functions such as heat capacity, entropy and Gibbs energy function have been computed in the temperature range 298–1,800 K.

Growth and Characterization of EuTiO3 Single Crystals

Bulk single crystal of the antiferromagnetic quantum paraelectric Europium Titanate was grown by using a floating zone technique. Magnetization and x-ray powder measurements found antiferromagnetic and structural transitions at temperatures consistent with existing literature. X-ray diffraction showed that single domain macroscopic samples of high quality were obtained.

Crystal Structures of New Compounds Na<sub>0.5</sub>Sm<sub>4.5</sub>Ti<sub>4</sub>O<sub>15</sub> and Na<sub>0.5</sub>Eu<sub>4.5</sub>Ti<sub>4</sub>O<sub>15</sub>

New compounds of sodium samarium titanate Na0.5Sm4.5Ti4O15and sodium europium titanate Na0.5Eu4.5Ti4O15were synthesized successfully by solid state reaction at 1300 oC and 1200 oC, respectively. The lattice parameters of Na0.5Sm4.5Ti4O15and Na0.5Eu4.5Ti4O15were determined at ordinary temperature by using X-ray powder diffraction method. Their Lattice types were determined, and their patterns were indexed. Polycrystalline X-ray diffraction data of sodium samarium titanate were listed. Differences of their crystal structures were analyzed and discussed.

Solution precursor synthesis and magnetic properties of Eu 1−xCa xTiO 3

Europium titanate, EuTiO 3, is a paraelectric/antiferromagnetic cubic perovskite with T N=5.5 K. It is predicted that compressive strain could induce simultaneous ferroelectricity and ferromagnetism in this material, leading to multiferroic behavior. As an alternative to epitaxial strain, we explored lattice contraction via chemical substitution of Eu 2+ with the smaller Ca 2+ cation as a mechanism to tune the magnetic properties of EuTiO 3. A modified sol–gel process was used to form homogeneously mixed precursors containing Eu 3+, Ca 2+, and Ti 4+, and reductive annealing was used to transform these precursors into crystalline powders of Eu 1− x Ca x TiO 3 with x=0.00, 0.05, 0.10, 0.15, 0.25, 0.35, 0.50, 0.55, 0.60, 0.65, 0.80, and 1.00. Powder XRD data indicated that a continuous Eu 1− x Ca x TiO 3 solid solution was readily accessible, and the lattice constants agreed well with those predicted by Vegard's law. SEM imaging and EDS element mapping indicated a homogeneous distribution of Eu, Ca, and Ti throughout the polycrystalline sample, and the actual Eu:Ca ratio agreed well with the nominal stoichiometry. Measurements of magnetic susceptibility vs. temperature indicated antiferromagnetic ordering in samples with x≤0.60, with T N decreasing from 5.4 K in EuTiO 3 to 2.6 K in Eu 0.40Ca 0.60TiO 3. No antiferromagnetic ordering above 1.8 K was detected in samples with x>0.60.

Synthesis, characterization and thermal expansion studies on europium titanate (Eu 2TiO 5)

The lattice thermal expansion characteristics of europium titanate (Eu 2TiO 5) have been studied by measuring the lattice parameter by high temperature X-ray diffraction technique (HT-XRD) in the temperature range 298–1573 K. Percentage linear thermal expansion and mean linear thermal expansion coefficients were computed from the lattice parameter data. The percentage linear thermal expansion in the temperature range 298–1573 K along a, b and c axes are 1.05, 1.15 and 0.95 respectively.

비휘발성 메모리 소자응용을 위한 Eu 첨가량에 따른 BET 박막의 강유전 특성

The effect of Eu contents on the ferroelectric properties of <TEX>$Bi_{4-x}Eu_xTi_3 O_{12}$</TEX> (BET) thin films has been investigated. Bismuth Europium titanate thin films with a Eu contents were prepared on the <TEX>$Pt/Ti/SiO_2/Si$</TEX> substrate by metal-organic decomposition technique. The structure and the morphology of the films were analyzed using X-ray diffraction (XRD) and field emission scanning microscopy (FE-SEM), respectively. From the XRD analysis, it was found that BET thin films have polycrystalline structure, and the layered-perovskite phase is obtained when the Eu contents exceeds 0.2 (x > 0.2). Also, the ferroelectric characteristics of the BET thin films were found to be dependent on the Eu content. Particularly, the BET films doped with x = 0.75 show better ferroelectric properties (remanent polarization 2Pr = 60.99 C/<TEX>$cm^2$</TEX> and only a little polarization fatigue up to <TEX>$3.5{\times}10^9$</TEX> bipolar switching cycling) than those doped with other Eu contents.

Thermoelectric Properties of Lanthanum-Doped Europium Titanate

The thermoelectric properties of lanthanum-doped polycrystalline perovskite-type europium titanate were measured from room temperature to 900 K and compared to those of MTiO 3 (M = Ca, Sr, Ba). The differences in the titanates were calculated in terms of the differences of A-site ion and Ti-O distance that determined the covalent bonding strength. The A-site ion appeared to have little influence on the electrical properties. The small Ti-O(Ti) distance results in strong bonding and it causes high thermal conductivity together with high electrical conductivity. Europium titanate showed power factor similar to and thermal conductivity lower than those of the strontium titanate. Eu 0 . 9 La 0 . 1 TiO 3 showed the highest dimensionless figure of merit of 0.25 at 900 K.

The magnetic properties of EuLiH 3

The bulk magnetic properties of the cubic perovskite material, EuLiH 3, have been investigated and the results strongly suggest that it is a ferromagnet with T c = 38°K and θ c = +40°K. Thus EuLiH 3 is very likely a new semiconducting ferromagnet. The properties of EuLiH 3 are compared with those of EuTiO 3, also a cubic perovskite with a very similar lattice parameter (3·79 Å for EuLiH 3 and 3·90 Å for EuTiO 3) which is, however, antiferromagnetic below 5°K. This somewhat surprising difference is discussed in terms of the molecular field theory and the results of previous work on exchange interactions in divalent europium compounds especially the europous monochalcogenides and europium titanate as well. It is concluded that the major factor influencing the different magnetic behavior of EuLiH 3 and EuTiO 3 is the apparent absence of a negative near-neighbor interaction in the former which is prominent in the latter. It is suggested that this diminution of antiferromagnetic exchange in EuLiH 3 is due to the inability of H − with electron configuration 1 s 2 to participate in super-exchange interactions to the same degree as O 2− with electron configuration (He)2 s 2 2 p 6.

Magnetic Structure of EuTiO3

Europium titanate has the cubic perovskite structure containing divalent Eu (7 μB) and tetravalent Ti. From magnetic measurements we find that EuTiO3 is one of the few antiferromagnetic materials with a positive θ (TN=5.3°K, θ=3.8°K). At 1.3°K the magnetic moment (σ) increases linearly with field to 10 kOe; above 14 kOe the moment saturates and σ=156 emu/gm (6.93 μB) at 20 kOe. Powder neutron-diffraction work indicates that EuTiO3 has the Type G magnetic structure in which a given Eu++ has six nearest-neighbor europium ions antiparallel and 12 next-nearest-neighbor europium ions parallel. In a perovskite structure where only the 12-coordinated ion is magnetic, i.e., Eu++, the molecular field relations for a two sublattice model yield J1/k=−0.021°K, where J1 is the effective intersublattice exchange interaction, and J2/k=0.040°K, where J2 is the effective intrasublattice exchange interaction. The signs of J1 and J2 are opposite to those found in the europium chalcogenide series. The chalcogenides, however, have the rocksalt structure in which the number of 90° cation-anion-cation interactions differs from the perovskite structure.