Samarium Titanate Research Articles

Tetrabutylammonium hydroxide mediated sol-gel synthesis of samarium titanate to enhance photocatalytic activity

To obtain photocatalytically active materials with increased porosity, tetrabutylammonium hydroxide (TBAOH) was applied to synthesize the samarium titanate. All the Sm2Ti2O7(v) samples have a solely pyrochlore samarium titanate crystal phase, and the crystallite size of Sm2Ti2O7 decreases from 39.1 nm to 19.5 nm with increasing TBAOH volume in the sol. The porosity of the Sm2Ti2O7(v) samples is significantly promoted after using TBAOH, and Sm2Ti2O7(1.0) has the maximum BET surface area of 12.67 m2/g and the maximum pore volume of 0.0271 cm3/g. The bandgap energy for the Sm2Ti2O7 is 3.41 eV, and the bandgap energies for Sm2Ti2O7(0.4), Sm2Ti2O7(1.0) and Sm2Ti2O7(1.4) are 3.61, 3.69 and 3.79 eV, respectively. The Sm2Ti2O7(v) samples can only respond to UV irradiation. Sm2Ti2O7(1.0) has the lowest photoluminescence intensity, indicating the lowest recombination efficiency for the electrons and holes. More Sm2+ exists in Sm2Ti2O7(1.0) prepared using TBAOH. The degradation efficiency of RBR X-3B is drastically enhanced with increasing TBAOH volume, and the maximum degradation efficiency is obtained for Sm2Ti2O7(1.0). The photocatalytic efficiency is 77.1% after 60 min of reaction for Sm2Ti2O7(1.0), and the overall dye removal efficiency is 96.6%. 82.5% of the original activity for Sm2Ti2O7(1.0) is maintained in the fourth reaction cycle.

Исследование структуры и свойств механоактивированного титаната самария

The relevance of the work is explained by the need to improve the quality of metal raw materials for the production of products with special properties, for example, in mining when leaching metals from ores, allowing to increase the extraction of components with a higher content in concentrates while minimizing the content of impurities. The purpose of the work. Substantiation of the possibility of changing the structure and properties of samarium titanate powder by processing in a spherical planetary mill "Activator 2S" due to the need to increase the purity of powders. Research methods: systematization, generalization and analysis of theoretical and experimental studies. To study the properties of samarium titanate, the following methods were used: scanning electron microscopy, X-ray phase, chemical, low-temperature nitrogen adsorption, X-ray phase analysis, spectral and atomic absorption with the processing of the results by methods of mathematical statistics. Results. The results of the study of the structure and properties of samarium titanate powders obtained by mechanochemical synthesis using a spherical planetary mill are presented. It is shown that the elemental composition of the mechanochemically synthesized charge corresponds to the stoichiometric content of titanium oxide and samarium. Quantitative values of activation parameters are given. The time of transformation of the initial oxides into nanocrystalline samarium titanate has been determined. The phases of the transformation of samarium titanate from an amorphous state to a crystalline state under the influence of temperature are differentiated. The properties of the samarium titanate powder obtained by mechanosynthesis are given. The possibility of obtaining nanoamorphic powder of samarium titanate by mechanochemical treatment of samarium and titanium oxides of the desired condition is proved.

Samarium titanate (Sm2Ti2O7) materials for high-temperature sensor applications

Samarium titanate (Sm2Ti2O7) is a perovskite layered structure (PLS) material with high Curie temperature (TC ​≥ ​1247 ​°C). Sm2Ti2O7 (STO) powders were synthesized by solid state reaction method by calcining the constituent powders at 1100 ​°C for 2 ​h. The average crystallite size of calcined STO powder was measured to be 61 ​nm. Circular discs of STO samples were sintered between the temperature range 1250–1450 ​°C with a soaking time of 2 ​h and sintered density was highest (>96.35% Th.) for the samples sintered at 1450 ​°C. The direct current electrical resistivity linearly decreased from 1013 to 106 ​Ω.cm during its increase in temperature from 100 to 900 ​°C. The activation energy of the STO samples were 0.38 ​± ​0.01 ​eV (Ea1) and 1.77 ​± ​0.01 ​eV (Ea2) at temperature ranges 100 to 400 ​°C and 500 to 900 ​°C, respectively. Hence, samarium titanate is a promising sensor material for high-temperature applications.

Facile synthesis of nanosized samarium titanate (Sm2Ti2O7) powders: structural, composition, thermal stability, optical and magnetic properties

Samarium titanate nanopowders have been successfully synthesized from their corresponding precursors through a facile modified sol–gel route.

Structure and properties of pure and zirconium substituted nanocrystalline samarium titanate

This study deals with the changes in the electrical and optical properties of Sm2Ti2O7 due to the substitution of 25 wt% of Zr with Ti. Nanocrystalline Sm2Ti2O7 and Sm2Ti1.5Zr0.5O7, with cubic pyrochlore structure, are prepared through the modified combustion technique. X-ray diffraction (XRD) is used to find the structure and confirmed using vibrational spectroscopic tools. The particle size obtained for Sm2Ti2O7 using the transmission electron microscopic technique (TEM) is 12.74 nm. The band gap energy values of Sm2Ti2O7 are 3.33 eV and for Sm2Ti1.5Zr0.5O7 it is 3.47 eV. The photoluminescence (PL) spectroscopic studies give emission around 569 nm. The average grain size obtained using scanning electron microscopy (SEM) is 0.13 μm and 0.27 μm for Sm2Ti2O7 and Sm2Ti1.5Zr0.5O7, respectively. The conductivity is increased with temperature and high conductivity of 2.27 × 10−2 S/m is obtained for Sm2Ti2O7. These materials are found suitable for optical and solid oxide fuel cell applications.

Crystal structure, morphology and optical behaviour of sol-gel derived pyrochlore rare earth titanates RE2Ti2O7 (RE=Dy, Sm)

Nanoscaled pyrochlore rare earth titanates RE2Ti2O7 (RE = Dy, Sm) were prepared by soft-chemical sol-gel route followed by thermal treatment. Dysprosium and Samarium precursors with two compositions (0.3 and 0.5 mol) were taken separately to synthesize rare earth titanates. The size and micro-structure of prepared titanates were analyzed through X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy and Transmission electron microscopy (TEM). Pyrochlore structure of rare earth titanates (Dy2Ti2O7 and Sm2Ti2O7) was successfully developed as confirmed by XRD. It was found that each reflection peak corresponding to pyrochlore structure shifted slightly towards the lower angle in case of Sm2Ti2O7 due to larger ionic radii of Sm3+ ion as compared to Dy3+ ion. The lattice constant of samarium titanate was found to be larger than that of dysprosium titanate. TEM images showed that the crystallites of prepared titanates with good dispersion were found to be almost spherical in shape with average size in range 33–40 nm. The optical band gap and emission wavelength were determined via UV–visible absorption and photoluminescence spectroscopy. The band gap of prepared titanates was increased on increasing the concentration of rare earth precursors (Dy/Sm), while the emission peak intensity was decreased.

Synthesis and Characterization of Nanocrystalline Barium–Samarium Titanate

Abstract Barium–samarium titanate nanopowder (Ba0.85 Sm0.1TiO3) was synthesized through tartrate precursor route. The effect of annealing temperature on the formation, crystalline size, morphology and magnetic properties was systematically studied. The annealing temperature was varied from 600°C to 1,100°C. Thermal analysis measurement (TG-DSC, thermogravimetry-differential scanning calorimetry) was carried out on the precursor to characterize the thermal decomposition behavior. The results showed that the precursor of Ba–Sm–Ti mixture decomposed thermally in multistep weight loss up to about 480°C and perovskite Ba0.85Sm0.1TiO3 started to form at ~520°C. X-ray diffraction and Fourier transform infrared (FTIR) spectroscopic measurements showed that the synthesized Ba0.85Sm0.1TiO3 has a tetragonal dominant structure with the presence of intermediate SmTi2O3 at lower annealing temperature. The ratio of SmTi2O3 was decreased and completely disappeared at higher annealing temperatures. The tetragonality, the theoretical density and the crystalline size were increased by increasing annealing temperature. The crystalline size is still in nano-range of 12.4–19.9 nm even after annealing at 1,100°C. The morphology of the produced sample transferred from nano-cubes to nano-whisker to nano-mace (nano-aggregates) with the increase of annealing temperature.

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.

Heat capacity and thermal expansion of samarium titanate

Samarium titanate (Sm2TiO5) was prepared by solid-state synthesis and characterized by X-ray diffraction (XRD). Heat capacity measurements were carried out by differential scanning calorimeter (DSC) in the temperature range 298–800K. Thermal expansion characteristics have been studied by high temperature X-ray diffraction technique (HTXRD) in the temperature range 298–1573K. The heat capacity value at 298K is 170JK−1mol−1. The percentage linear thermal expansion in the temperature range 298–1573K along a, b and c axes are 0.96, 0.89 and 1.07 respectively. The average coefficient of thermal expansion value obtained in the present study for samarium titanate up to 1573K is 10.8×10−6K−1.

Percolation phenomenon in barium samarium titanate–silver composite

Ba 4Sm 9.33Ti 18O 54–Ag (BST–Ag) composites were prepared by a solid-state ceramic route and its dielectric properties were investigated in the vicinity of percolation threshold. The structure and microstructure of the composites were analyzed by X-ray diffraction along with optical and scanning electron microscopy observations. The effects of silver content and frequency on the dielectric properties of BST–Ag composites were studied using a LCR meter. The relative permittivity ( ε r) of the composite increases with silver content below the percolation limit and is in agreement with power law. A 0.14 volume fraction of silver loading increases the relative permittivity of the composite from 50 to 450 at 10 kHz. Addition of 0.15 volume fraction of silver increases the relative permittivity of the composite in the order of 10 5. It is found that the giant relative permittivity is almost constant for frequencies from 1 kHz to 1 MHz. This high ε r composite offers the perspectives for application in electromechanical devices.

An insight into the theoretical investigation of possible piezoelectric effect in samarium titanate (SmTiO3)

Abstract The perovskite structure is the most important piezoelectric crystalline structure. In this paper, the Douglas–Kroll–Hess second-order scalar relativistic method is applied for investigation of the possible piezoelectricity in the samarium titanate (SmTiO3). Initially, to aim at an adequate representation of the many-electron environment of SmTiO3 through a very good description of the total and the orbital energies (eHOMO and eHOMO−1) of the system’s constituent fragments, the generator coordinate HF (GCHF) method was applied to build Gaussian basis sets, which were contracted to (25s16p)/[5s4p] for the O (3P) atom, to (29s18p12d)/[9s5p3d] for the Ti (5S) atom, and to (32s22p16d10f)/[16s11p7d3f] for Sm (7F) atom and after supplementation with polarization and diffuse functions, they were used to investigate the property of interest in the considered system. The calculations and the analysis of total energy, dipole moment and atomic charges evidence that the possible piezoelectric effect in the SmTiO3 is caused by electrostatic interactions.

Damage evolution on Sm and O sublattices in Au-implanted samarium titanate pyrochlore

Damage evolution on the Sm and O sublattices in Sm2Ti2O7 single crystals irradiated with 1 MeV Au2+ ions at 170, 300, and 700 K was studied by Rutherford backscattering spectroscopy and O16(d,p)17O nuclear reaction analysis along the 〈001〉 direction. The damage accumulation behavior at each irradiation temperature indicates that the relative disorder on the O sublattice is higher than that on the Sm sublattice, and the relative disorder, determined by ion channeling, on each sublattice follows a nonlinear dependence on dose that is well described by a disorder accumulation model. While there is little difference in damage accumulation behavior on the Sm sublattice at 170 and 300 K irradiation, the rate of damage accumulation decreases dramatically at 700 K due to dynamic recovery processes. The critical dose for amorphization at 170 and 300 K is 0.14 displacements per atom (dpa), and a higher dose of 0.22 dpa is observed under irradiation at 700 K. During thermal annealing in an O18 environment, a significant increase in the O18 exchange was observed between 800 and 900 K, which is just below the previously determined critical temperature, 950 K, for amorphization in Sm2Ti2O7, suggesting that the mobility of O vacancies may be important in defining the critical temperature.

Damage accumulation and amorphization in samarium titanate pyrochlore

Damage accumulation in Sm 2Ti 2O 7 single crystals irradiated with Au 2+ ions at 170, 300 and 700 K was studied by Rutherford backscattering spectrometry using a 2.0 MeV He + beam along the 〈0 0 1〉 channeling direction. The relative disorder on the Sm sublattice follows a nonlinear dependence on ion fluence. The nonlinear behavior is described well by a disorder accumulation model that indicates a predominant role of a defect-stimulated amorphization process. The critical dose for amorphization at 300 K is ∼0.14 dpa, which is in good agreement with in situ transmission electron microscopy results for polycrystalline Sm 2Ti 2O 7 irradiated with 600 keV Bi + ions and with Gd 2Ti 2O 7 doped with 244Cm. Despite the six orders of magnitude difference in damage rates, the good agreement between the amorphization doses in Sm 2Ti 2O 7 at 300 K and 244Cm-doped Gd 2Ti 2O 7 at 340 K indicates that damage accumulation at these temperatures is relatively independent of dose rate.

Damage Evolution and Annealing of Au-Irradiated Samarium Titanate Pyrochlore

ABSTRACTDamage evolution and thermal recovery of 1 MeV Au2+ irradiated samarium titanate pyrochlore (Sm2Ti2O7) single crystals were studied by Rutherford backscattering spectroscopy and nuclear reaction analysis. The damage accumulation follows a nonlinear dependence on dose that is well described by a disorder accumulation model, which indicates a predominant role of defect-stimulated amorphization processes. The critical dose for amorphization at 170 and 300 K is ∼0.14 dpa, and a higher dose of ∼ 0.22 dpa is observed for irradiation at 700 K, which agrees with previous in-situ transmission electron microscopy (TEM) data for polycrystalline Sm2Ti2O7. Annealing in an 18O environment reveals a damage recovery stage at ∼ 850 K that coincides with a significant increase in 18O exchange due to oxygen vacancy mobility. This thermal recovery stage is also consistent with the critical temperature for amorphization measured by in-situ TEM in polycrystalline samples.