Combustion Synthesis of Double Phosphates

The composition of combustion products of calcium hypophosphite Ca(H₂PO₂)₂ in air at atmospheric pressure using sodium or potassium nitrates or nitrites as oxidizers was studied. Synthesis was carried out to obtain double phosphate of the composition Na(K)CaPO₄. Mixtures of powders with zero oxygen balance were prepared using, if necessary, an additional amount of ammonium nitrate. The phase composition of condensed combustion products was studied by X-ray powder analysis. At atmospheric pressure, the mixtures burned steadily with the release of P₄O₁₀ aerosol. The combustion products were melted white particles up to 1 mm in size. The condensed combustion products were found to contain the double phosphates NaCaPO₄, Na₂CaP₂O₇, K₂CaP₂O₇, and KCaPO₄ and calcium pyrophosphates Ca₂P₂O₇.