Determination of the thermodynamic stability of TiB2

Abstract

The standard free energy of formation of titanium boride (TiB2) was measured by the Electro Motive Force (EMF) method (by using yttria doped thoria (YDT) as the solid electrolyte). Two galvanic cells viz. Cell (I): Pt, TiB2 (s), TiO2 (s), B (s) |YDT| NiO (s), Ni (s), Pt and cell (II): Pt, TiB2 (s), TiO2 (s), B (s) |YDT| FeO (s), Fe (s), Pt were constructed in order to determine the ΔfG° of TiB2. Enthalpy increments on TiB2 were measured by using inverse drop calorimetry over the temperature range 583–1769 K. The heat capacity, entropy and the free energy function have been derived from these experimental data in the temperature range 298–1800 K. The mean value of the standard enthalpy of formation of TiB2 (ΔfH298∘ 〈TiB2〉) was obtained by combining these ΔfG° values and the free energy functions of TiB2 derived from the drop calorimetry data. The mean values of ΔfH298∘ 〈TiB2〉 derived from the ΔfG° data obtained from cell I and II were −322 ± 1.2 kJ mol−1 and −323.3 ± 2.1 kJ mol−1, respectively. These values were found to be in very good agreement with the assessed data.