Rasna Thakur

Dielectric, magnetic, and thermodynamic properties of Y1−xSrxMnO3 (x = 0.1 and 0.2)

We report the effect of strontium (Sr) doping on dielectric, magnetization, and thermodynamic properties of polycrystalline Y1−xSrxMnO3 (x = 0.1, 0.2) samples prepared by conventional solid-state reaction method. The temperature dependent dielectric permittivity and specific heat curves noticeably show the anomalies near its magnetic transition point, i.e., Neel temperature (TN), which are probably generated by the frustrated Mn3+ spins (S = 2) on a triangular Mn lattice showing the magneto-electric coupling between the electric and magnetic orders. However, the magnetic transition is not clearly evident in the magnetic susceptibility due to the frustration on the Mn triangular lattice and the dominating paramagnetic susceptibility of the Y3+ spins. The electronic transport mechanism in these materials was analyzed within the framework of conventional Arrhenius Law, i.e., ρ(T) = C exp(Ea/kBT) applied to low frequency ac resistivity data, and through the peak method employed to the permittivity and loss ta...

Thermodynamic properties of BaRuO3

We have investigated the specific heat, thermal expansion and thermodynamic properties of BaRuO3 in rhombohedral, hexagonal and cubic phase using the modified rigid ion model (MRIM) by incorporating the effect of lattice distortions. The calculated Debye temperature, specific heat and other thermal properties reproduce well with the available experimental data, implying that MRIM represents properly the nature of the perovskite-type BaRuO3. Besides, we have reported the thermal expansion (α), bulk modulus (B), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ D), and Gruneisen parameter (γ).

Specific heat and thermal expansion of La1−xEuxCoO3

We have investigated the specific heat and thermal expansion of La1−xEuxCoO3 (0.0 ≤ x ≤ 1.0) perovskite using a modified rigid ion model for the temperature range 1 K ≤ T ≤ 1000 K. The trends of variation in our computed specific heats and thermal expansion are in good agreement with corresponding experimental data for almost all the compositions (x). The specific heat is found to increase with temperature from 15 to 300 K, while it decreases with concentration (x) for these perovskite cobaltates. In addition, the results on the temperature dependence of the molecular force constant (f), Reststrahlen frequency (υ), cohesive energy () and Debye temperature (θD) are also discussed.

Bulk modulus and specific heat of B-site doped (La0.3Pr0.7)0.65Ca0.35Mn1−xBxO3 (B=Fe, Cr, Ru, Al, Ga)

Specific heat (Cp) thermal expansion (α) and Bulk modulus (BT) of lightly doped Rare Earth manganites (La0.3Pr0.7)0.65Ca0.35Mn1−xBxO3 (B3+ = Fe3+,Cr3+,Ga3+,Al3+,Ru4+); (0.3<x<0.10) has been studied by means of a Modified Rigid Ion Model (MRIM) and AIM theory using a atomistic approach. The partial replacement of B-site cation by other transition / Group IIIA elements of different size, mass and valence introduces large size and charge mismatch at B-site affecting the bulk modulus and thermal properties. Lattice specific heat (Cp)lat of (La0.3Pr0.7)0.65Ca0.35Mn0.97Fe0.03O3 as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

ELASTIC AND THERMAL PROPERTIES OF Sr1-xCaxRuO3

We have investigated the elastic and thermal properties of Sr1-xCaxRuO3(0≤x ≤1) perovskite using a modified rigid ion model (MRIM). The trend of variation of our computed specific heat in the temperature range 1 K ≤ T ≤ 1000 K are in good agreement with corresponding experimental data for almost all the compositions (x). The specific heat found to increase with temperature from 1 K to 300 K, while they decrease with concentration (x) for these perovskite ruthenates. Besides, we have reported the thermal properties, like thermal expansion (α), molecular force constant (f), Reststrahlen frequency (υ), cohesive energy (ϕ), Debye temperature (θD) and Gruneisen parameter (γ).

Elastic and thermal properties of Sr1−xYxCoO3

ABSTRACT The elastic and thermal properties of Sr1−xYxCoO3 (0 ≤ x ≤ 0.5) have been investigated, probably for the first time, by using modified rigid ion model. We present the elastic constants (C11, C12, C44) and other elastic properties like bulk modulus (B), Youngs modulus (Y), shear modulus (G), Poissons ratio (σ), Lames parameter (μ, λ), transverse, longitudinal and average wave velocity (υt, υl and υm) and anisotropy parameter (A). Besides, we have reported the thermodynamic properties molecular force constant (f), Reststrahlen frequency (υ), cohesive energy (φ), Debye temperature (θD) and Gruneisen parameter (γ). We have also computed the variation of specific heat (C) and volume thermal expansion coefficient (α). The computed results on the elastic and thermodynamic properties are the first report on them. This model is capable of explaining the Cauchys discrepancy, elastic and thermal properties successfully.

Thermal expansion and specific heat of a superior IR-SOFC cathode material Sr1-xCexCoO3-δ

We present the specific heat (Cv) and thermal expansion (α) of lightly doped Sr1-xCexCoO3-δ (x=0.0-0.15) using Modified Rigid Ion Model (MRIM) and a novel atomistic approach of Atom in Molecules(AIM) theory. We partial replaced the A-site Strontium cation by other element (Cerium) of different size, valence and mass. The effect of Cerium doping on lattice specific heat (Cv)lat, thermal expansion(α) of Sr1-xCexCoO3-δ (x = 0.0-0.15) as a function of temperature (20K≤T≤ 1000K) is reported probably for the first time. The results indicate better thermal compatibility of Sr0.95Ce0.05CoO3 with Samaria doped Ceria (SDC) electrolyte than other studied compounds. The Debye temperature of these perovskite material as cathode for Intermediate Range Solid Oxide Fuel Cell (IR-SOFC) is also predicted.

Magnetic transition in Y-site doped multiferroic YMnO3

We have synthesized polycrystalline hexagonal Y1-xSrxMnO3 (x=0.02, 0.1) compounds by using conventional solid state reaction method. The detailed structural investigations are carried out by using XRD studies which reveals the single phase formation of the reported compounds with hexagonal structure and space group P63cm (JCPDS: 25-1079). Further the XRD data of reported compounds were analyzed by RIETVELD (FULLPROFF) method which shows the decrease in the lattice parameter with increasing concentration of divalent strontium to Y-site. The observed pointed kinks in the specific heat study are indicative of the probable coupling in between the electric and magnetic orders in this class of materials. The reported systematic specific heat studies shows that the antiferromagnetic (AFM) transition temperature (TN) shifts to higher value with increasing concentration of Sr2+ ion in the YMnO3 compound which is attributed to the enhanced lattice contribution to the specific heat in the this compound. The present compound shows the independence of specific heat and magnetic transition temperature with applied magnetic field of 8T and 12T.

Thermodynamic properties of Ba1-xLaxCoO3

We have predicted the thermodynamic behavior of Ba1-xLaxCoO3 family at temperature 1K≤T≤300K using the Modified Rigid Ion Model (MRIM). The specific heat of BaCoO3 with La doping in the perovskite structure at A-site has been reported. Also, the cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θD), specific heat (C) and Gruneisen parameter (γ) of Ba1-xLaxCoO3 compounds are discussed.

The effect of Ca doping on specific heat of YCoO3 cobaltate

We have investigated the thermodynamic properties of Y1-xCaxCoO3 (0.0≤x≤0.1) perovskites by means of a modified rigid ion model (MRIM). The variations of specific heat at wide temperatures 1 K ≤ T ≤ 1000 K are reported. Also, the effect of lattice distortions on the elastic and thermal properties of pure and Ca doped cobaltates has been studied by an atomistic approach. Besides, we have reported bulk modulus (B), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ D ), Gruneisen parameter (γ) and specific heat (C). It is found that the present model has a promise to predict the thermodynamic properties of other perovskites as well.