The heat capacity of bismuth silicates

• Heat capacity of Bi12SiO20 was studied by DSC method (ASM E1269).
• Heat capacity of Bi4Si3O12 was studied by DSC method.
• Standard entropy, S298°, of Bi12SiO20 and Bi4Si3O12 compounds were estimated.

Investigations of the thermodynamic properties of bismuth silicate stable compounds is of practical importance in a view of their valuable properties. The heat capacity of Bi12SiO20 and Bi4Si3O12 compounds in temperature range from 330 K to 1135 K has been determined. The modified Debye function was employed to describe the low-temperature heat capacities, and from the obtained function, the standard entropy, S298°, of bismuth silicates Bi12SiO20 and for Bi4Si3O12 were estimated as 15.7 ± 2.2 J/mol atoms K−1 and 13.9 ± 1.5 J/mol atoms K−1, respectively. A three-term Maier–Kelley polynomial representation, a + b × T + c × T−2 was used above 298 K to describe the heat capacity data.