Peculiarities of thermal solid-phase transformations of hydrogenphosphates Co(II)-Mn(II)

Abstract

Peculiarities of thermal solid-phase transformations of Co₁₋xMnxHPO₄·1.5 H₂O (0 ≤ x ≤ 0.45), which accompanying the formation of a final product of thermolysis - anhydrous diphosphate solid solution with composition β-(Co₁₋xMnx)₂P₂O₇ (0 < x le; 0.45) are established. It is shown that low-temperature α-modification of the diphosphate is the first formed during heat treatment of the hydrogenphosphates Co₁₋xMnxHPO₄·1.5H₂O with 0 <x ≤ 0.15. Crystalline β-(Co₁₋xMnx)₂P₂O₇ (x≤0.15) is formed only after the polymorphic transformation of the α-form into the β-form. The formation of β-(Co₁₋xMnx)₂P₂O₇ with 0.15 < x ≤ 0.45 occurs bypassing the α-form. Free phosphoric acid during the heat treatment Co₁₋xMnxHPO₄·1.5H₂O (0 < x ≤ 0.45) are is not formed.