MOLTEN-SALT PREPARATION OF K-ZR TERNARY PHOSPHATES

Mixed phosphates of K and Zr have been prepared by means of the reacti ons of hydrated ZrOCl2 and NH4H2PO4 salts with KNO3 in the temperature range 250-550 degrees C. Molten salt reactions were studied by thermo gravimetry and mass spectrometry of the evolved gases. Thermal analysi s of the ternary mixture demonstrated that a strongly exothermic mass loss occurs at ca. 250 degrees C, due to the reaction producing a KHZr (PO4)(2) phase. Depending on the reaction conditions, different solids can be obtained, including dispersed zirconia superficially doped wit h phosphate or crystalline ternary phosphates such as KZr2(PO4)(3) of NASICON structure or the layered compound K2Zr(PO4)(2). The solids obt ained were characterized by X-ray diffraction, H-1 and P-31 NMR spectr oscopy. A correlation of P-31 chemical shift and the mean electronegat ivity of the obtained solids has been proposed.