Phase equilibria in the Na2O-WO3 system

The Na2O-WO3 binary system is an important chemical system with various applications, such as catalysts, energy and corrosion resistant materials. In this study, phase equilibria and liquidus temperatures in the Na2O-WO3 binary system have been experimentally determined in air. The system was investigated at the temperature range from 550 to 830 °C using a high-temperature equilibration and quenching technique. The microstructure and compositions of the phases obtained in the quenched samples were then analyzed by an electron probe micro-analyzer (EPMA). Binary compounds Na2W2O7, Na2W4O13 and Na2W6O19 have been identified and the liquidus temperature temperatures in these primary phase fields were determined. Two peritectic points in the system were confirmed and compared with previous data. The present study provided useful thermodynamic data including liquidus and solid solutions. Accurate phase equilibria data will be used as the base for the development of thermodynamic modelling.