Heat capacity and thermodynamic functions of hollandite-type K0.17TiO1.9·0.061H2O

Abstract

The heat capacity of K0.17TiO1.9·0.061H2O has been measured by the use of a Quantum Design Physical Property Measurement System (PPMS) in the temperature range from 1.9 K to 302 K. An upturn below 3 K and weak bump at 7 K are observed and ascribed to Schottky anomaly and boson peak, respectively. The experimental data for K0.17TiO1.9·0.061H2O are fitted to a joint contributions of lattice vacancy, lattice vibration, Schottky anomaly and boson peak in the low temperature range (T < 9 K), orthogonal polynomials in the middle temperature range (9 < T < 63) K, and a combination of Debye and Einstein functions in the high temperature range (T > 63 K). The standard molar heat capacity, molar entropy, and molar enthalpy for K0.17TiO1.9·0.061H2O at T = 298.15 K are determined to be (64.2 ± 0.7) J·K−1·mol−1, (65.7 ± 0.7) J·K−1·mol−1, and (10.5 ± 0.1) kJ·mol−1, respectively, leading to a Gibbs energy of −(9.05 ± 0.09) kJ·mol−1.