Thermodynamic properties and X-ray diffraction of Bi4Ti3O12

The temperature dependence of heat capacity of Bi4Ti3O12 has been measured for the first time in the range from 7 to 346 K by precision adiabatic vacuum calorimetry. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity, enthalpy Ho(T) − Ho(0), entropy So(T) − So(0), and Gibbs function Go(T) − Ho(0), in the range from T → 0 to 346 K. The structure of Bi4Ti3O12 is refined by the Rietveld method (space group Fmmm, Z = 4) at temperatures of 173, 273, 373, 473 K. Thermal deformation model is proposed on the basis of structural data.