Low temperature heat capacity study of Ba₂TiSi₂O ₈ and Sr₂TiSi₂O₈

The heat capacities of powdered Ba₂TiSi₂O₈ and Sr₂TiSi₂O₈ have been measured over the temperature range from (2 to 300) K using a Quantum Design Physical Property Measurement System (PPMS). These two compounds have similar heat capacity values over the experimental temperature range because of their analogous structures. However, the heat capacities do display a crossover at T = 112.6 K, below which the heat capacity of Ba₂TiSi₂O₈ becomes larger than that of Sr₂TiSi₂O₈. The experimental data have been fitted to a series of theoretical functions from which the thermodynamic functions have been calculated. The standard molar entropies at T = 298.15 K have been determined to be (254.67 ± 2.55) and (252.61 ± 2.78) J·K^-1·mol^-1 for Ba ₂TiSi₂O₈ and Sr₂TiSi ₂O₈, respectively.