Some Properties and Sintering of Ca₂P₂O₇ Powders Obtained by Pyrolysis of CaHPO₄⋅2H₂O

Abstract

Some properties and sinterability of Ca₂P₂O₇ powders obtained by pyrolysis of reagent grade CaHPO₄⋅2H₂O were examined. The samples underwent relief of water of crystallization and then dehydration-condensation, while they still retained their original shapes. The heated samples consisted of agglomerated primary particles, which were comprised of smaller crystallites. The change in properties of powders during heat-treatment was explained in terms of rearrangement and growth of crystallites and neck growth between primary particles. The density of compacts increased in proportion to logarithm of pressure under a certain pressure, whilst it increased irregularly above this pressure with a smaller slope. The density of compacts and its pressure dependence were explained on the basis of three different types of void spaces during pressure treatment. Among the Ca₂P₂O₇ powders obtained at various temperatures, those heated at temperatures between 400°C and 600°C were found to sinter most densely.