The heat capacity of bismuth silicates

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, S-298 degrees, 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 x T+c x T-2 was used above 298 K to describe the heat capacity data. (C) 2014 Elsevier B.V. All rights reserved.