Synthesis of three-dimensional compounds from alkali-metal ion-exchanged γ-titanium phosphate

Abstract

Treatment of γ-titanium phosphate with 1 mol dm^–3 solutions of MCl (M = Na, K, Cs) results in layered crystalline phases with compositions at 50 °C of: γ-Ti(Na_0.5H_1.5PO₄)(PO₄)·H₂O, γ-Ti(KHPO₄)(PO₄)·½H₂O and γ-Ti(Cs_0.5H_1.5PO₄)(PO₄)·½H₂O. Heating at 900 °C gives rise to three-dimensional crystalline compounds. The composition of the new materials depends on the type of alkali-metal present in the solid. The K phase originates KTi₂(PO₄)₃, the Cs phase α-CsTi₃P₅O₁₉, and the Na phase produces mixtures of NaTi₂(PO₄)₃ and TiP₂O₇. Moreover, amorphous alkali-metal phosphates which are soluble in acidic media are formed. Samples of γ-Ti(KHPO₄)(PO₄)·½H₂O (A), KTi₂(PO₄)₃(B) and α-CsTi₃P₅O₁₉(C) have been studied using X-ray powder diffraction. The lattice parameters of A [a= 5.063(3)Å, b= 6.297(1)Å, c= 11.502(5)Å, β= 109.30(4)°], B [a= 8.3569(2)Å, c= 23.0725(3)Å] and C [a= 6.320(1)Å, b= 14.122(2)Å, c= 9.333(2)Å, β= 105.82(2)°] have also been calculated.