Phase equilibrium investigations and thermodynamic modelling of the ZrO2-Ta2O5 system.

Phase equilibria in the ZrO 2 -Ta 2 O 5 system were studied in the temperature range from 1673 K to 1973 K using equilibration technique and in the temperature range up to 2473 K using differential thermal analysis (DTA). Phase and chemical composition of the samples was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-Ray analysis (EDX). Melting relations were studied using DTA followed by microstructure investigation by means of SEM/EDX. The eutectic reaction was determined at 1994 K and composition of 51 ± 2 mol% Ta 2 O 5. It was found that the intermediate compound Zr 6 Ta 2 O 17 melts by peritectic reaction at 2166 K. The heat capacity of this compound was measured using differential scanning calorimetry (DSC) in three temperature ranges from 100 K to 230 K, from 220 K to 570 K and from 330 K to 1295 K. Based on the obtained results and literature data thermodynamic parameters of the quasibinary ZrO 2 -Ta 2 O 5 system were optimized using the CALPHAD approach. [ABSTRACT FROM AUTHOR]