Phase relations in the Ta2O5-WO3-SiO2 system

Abstract Subsolidus relations and liquidus boundaries in the Ta 2 O 3 -WO 3 -SiO 2 system at temperatures ranging from 1200 °C to 1500 °C were investigated. Phase diagrams were constructed. Compounds with stoichiometries of Ta 22 W 4 O 67 , Ta 2 WO 8 and Ta 16 W 18 O 94 formed in the Ta 2 O 5 -WO 3 subsystem at 1200 °C. SiO 2 was compatible with each of the compounds. A solid solution with a formula of (1 − x) Ta 2 O 5 ·xWO 3 formed on the Ta 2 O 5 -WO 3 line in the compositional range of Ta 2 O 5 :WO 3  > 11:4. SiO 2 had a maximum solubility of 25% SiO 2 in the solid solution. Liquid phase first appeared in the WO 3 -rich corner at 1300 °C. As the temperature was increased up to 1500 °C, the liquidus area boundary gradually expanded towards the SiO 2 - and the Ta 2 O 5 -rich corners.