Determination of thermodynamic stability of CrSbO 4 using oxide solid electrolyte

Abstract

An isothermal section of the phase diagram of the system Cr–Sb–O at 873 K was established by isothermal equilibration and X-ray diffraction analysis of quenched samples. Making use of the coexistence of the only ternary oxide CrSbO 4(s) identified in the system with Cr 2O 3(s) and Sb 2O 3(s,l), the galvanic cell Pt, Cr 2 O 3( s), Sb 2 O 3( s,l), CrSbO 4( s) |15 CSZ| air (P O 2 =0.21 atm), Pt (where 15 CSZ stands for 15 wt% CaO stabilized ZrO 2 electrolyte tube) was designed to measure its Gibbs energy of formation. The emf of the cell was measured over the temperature range 770–982 K. The results could be summarized by the expressions: E±0.5 ( mV)=874.25−0.45952 T ( K) (770–920 K), E±0.2 ( mV)=1003.58−0.59859 T ( K) (931–982 K). The break in the plot of emf as a function of temperature at 930 K yielded a value of 50 kJ mol −1 for the enthalpy of fusion of Sb 2O 3 in agreement with the literature. From the emf results the standard Gibbs energy of formation, ΔG 0 f (CrSbO 4), was calculated to be ΔG f 0 ( CrSbO 4)±4.1 ( kJ mol −1)=−1074.84+0.34002 T ( K) (770–920 K) and ΔG f 0 ( CrSbO 4)±4.0 ( kJ mol −1)=−1088.32+0.35365 T ( K) (931–982 K).