Molar heat capacity and thermodynamic functions of zirconolite CaZrTi₂O₇

Zirconolite (CaZrTi₂O₇) has been proposed as a host phase for excess weapons plutonium, and the standard molar entropy ΔA^{298.15 K}₀ S^o_m and other derived thermodynamic functions are needed to describe it completely. The heat capacity of CaZrTi₂O₇ has been measured from T ≈ 20 K to T ≈ 400 K with an adiabatic calorimeter. A six-term fitting equation based on Debye and Einstein functions has been shown to represent the heat capacity over the entire range of temperature to within the experimental uncertainty. This equation has been used to calculate the thermodynamic functions to T = 400 K and to extrapolate these functions to T = 1500 K. In particular, Δ^{298.15 K}₀ S^o_m for CaZrTi₂O₇ is 193.3 J · K^-1 · mol^-1.