Molar heat capacity and thermodynamic functions of zirconolite CaZrTi2O7

Zirconolite (CaZrTi2O7) has been proposed as a host phase for excess weapon s plutonium. and the standard molar entropy Delta(0)(298.15 K) S-m(o) and o ther derived thermodynamic functions are needed to describe it completely. The heat capacity of CaZrTi2O7 has been measured from T approximate to 20 K to T approximate to 400 K with an adiabatic calorimeter. A six-term fittin g equation based on Debye and Einstein functions has been shown to represen t the heat capacity over the entire range of temperature to within the expe rimental uncertainty. This equation has been used to calculate the thermody namic functions to T = 400 K and to extrapolate these functions to T = 1500 K. In particular, Delta(0)(298.15 K)S(m)(o) for CaZrTi2O7 is 193.3 J . K-1 . mol(-1). (C) 1999 Academic Press.