Influence of calcination temperature of acidic ammonium salts of phosphotungstic acid on their composition and properties

Abstract The effect of the calcination temperature on the structure and properties of acidic ammonium salt (NH4)2HPW12O40 was studied. The absence of the influence of the calcination temperature of the samples on their particle size distribution, thermal stability and water content was shown. In the investigated range from 300 to 450 ​°C, a nonmonotonic change in the specific surface area and proton-conducting properties is observed depending on the calcination temperature. Calcination at a temperature other than optimal leads to a decrease in the specific surface area and proton conducting properties. A lower temperature is probably not enough for a complete redistribution of protons and ammonium ions; and an increase in the calcination temperature above optimal one entails the compaction of the salt crystallites.