Phase relations in the CaTa2O6-LaTa3O9 system

Phase relations in the CaTa2O6-LaTa3O9 system were studied between 1200 deg rees C and liquidus temperatures. The character of the CaTa2O6 polymorphism was refined. Two high-temperature modifications of CaTa2O6 were identified : tetragonal (alpha(1)) phase (a = 3.882 Angstrom, c = 7.828 Angstrom), sta ble from 1450 to 1650 degrees C, and cubic (alpha(2)) phase (a = 7.758 Angs trom), stable from 1650 degrees C to the melting point. These perovskite ph ases were found to dissolve up to similar or equal to 20 mol % LaTa3O9. An orthorhombic perovskite phase Ca(1-x)/2Lax/3TaO3 (x = 0.33-0.47 at 1600 deg rees C), stable over the whole temperature range studied, was identified. L aTa3O9 was shown to dissolve up to 40 mol % CaTa2O6.