Thermodynamic and Electrophysical Properties of La₂SrNiTeO₇

The isobaric heat capacity of nickelite-tellurite La₂SrNiTeO₇ was studied by calorimetry at 298.15–673 K. λ-Shaped effects related to the second-order phase transition were revealed for the compound in the given temperature range. The equations of the temperature dependence of the heat capacity were derived taking into account the transition temperatures. The temperature dependences of the heat capacity, entropy, enthalpy, and reduced thermodynamic potential were calculated from the experimental heat capacities and calculated standard entropies of nickelite-tellurite. The temperature dependences of the dielectric constant and electric resistance of nickelite-tellurite at 293–483 K were studied. The curves of the dependences $\log \epsilon =f\left(T\right)$ and $\log R=f\left(T\right)$ have maxima and minima, which confirm the λ-shaped effects related to the second-order phase transition on the curve of $C_p^{\circ }=f\left(T\right)$ for the compound.