A RE-EXAMINATION OF SYSTEM NB2O5-TIO2 AT LIQUIDUS TEMPERATURES

The liquidus curve for the system Nb2O5-TiO2 has been determined by means of the Griffin-Telin hot-stage microscope. The shape of the curve confirms the existence of the compounds 5Nb2O5.2TiO2 and Nb2O5.TiO2, which melt congruently at 1488 ° and 1498 °C, respectively. The existence of a compound with the composition 3Nb2O5.2TiO2 is also indicated. It melts congruently at 1486 °C. The results of X-ray diffraction analysis of samples quenched from 1350 ° and 1450 °C, combined with those of differential thermal analysis, suggest that the compound 3Nb2O5.2TiO2 is stable only above 1425 °C. The melting temperature of Nb2O5 has been determined to be 1507 °C. The previously published value of 1483 °C appears to be a transition temperature between two forms of Nb2O5. © 1969.