Exploration of YPO4 as a potential environmental barrier coating

A non-silicate material, yttrium phosphate (YPO4), is developed for the application as environmental barrier coatings. The key issues of environmental durability, phase stability, chemical compatibility, and coefficient of thermal expansion (CTE) are considered for the selection of YPO4. The water corrosion behaviors for the sol–gel prepared YPO4 were investigated in an atmosphere of 50% H2O–50% O2 water vapor at 1350 °C. The hot corrosion study of YPO4 was carried out at 900 °C with Na2SO4 melt. The results demonstrate that YPO4 has excellent environmental durability. During these tests, YPO4 had no phase change and decomposition. Moreover, the reactions between YPO4 and silica at high temperatures were not detected, indicating the good chemical compatibility of YPO4. The measured CTE of YPO4 is close to that of SiC. The suitable CTE, good environmental durability and chemical compatibility, and excellent phase stability of YPO4 indicate that it is a potential environmental barrier coating material.