Isobaric heat capacity and standard thermodynamic properties of NaLaTiO4 and Na2La2Ti3O10 over the range of (7–670) K

Abstract

The heat capacities of layered perovskite-like oxides NaLaTiO4 and Na2La2Ti3O10 were measured by precision adiabatic vacuum calorimetry over the temperature range of (7–350) K and by differential scanning calorimetry over the temperature range of (350–670) K. The standard thermodynamic functions: molar heat capacity C p,m, enthalpy H(T) − H(9), entropy S(T) − S(9), and Gibbs energy −[G(T) − G(9)] of the compounds were evaluated from the experimental heat capacity temperature dependences over the range of (9–670) K. The extrapolation of heat capacity down to T = 0 K is incorrect in this case due to the considerable deviation of experimental points from fitting curves obtained on the basis of Debye’s theory.