REACTIONS OF THE ALKALINE-EARTH METAL PYRO-VANADATES AND ORTHOVANADATES WITH AMMONIA

Reactions of the alkaline earth metal vanadates A2V2O7 and A3V2O8 (A- Ca, Sr, Ba) with hydrogen and ammonia have been investigated by thermo gravimetric analysis and in a flow reactor. Reactions in ammonia do no t lead to the formation of oxynitride phases, in contrast with the for mation of LaVO3-xNx from LaVO4 under similar conditions. Both hydrogen reduction and ammonia reactions of the A2V2O7 compounds are dominated by the formation of the corresponding A3V2O8 phases. Ba3V2O8 and Sr3V 2O8 do not react easily in ammonia at temperatures below 1000-degrees- C and Ca3V2O8 converts to CaO and VN or to CaO, VN and CaVO3.