THE SYNTHESIS OF CRYSTALLINE ZIRCONIUM PHOSPHATE WITH LARGE PARTICLE SIZE BY THE DIRECT-PRECIPITATION METHOD

The direct-precipitation method was studied as a possible way to synthesize crystalline zirconium phosphate of a large and uniform crystal size. The yield and the crystal size were examined as functions of the initial hydrofluoric-acid and phosphoric-acid concentrations and the warming temperature. The conditions for preparing the largest crystal were: ZrOCl2·8H2O, 0.13 M; hydrofluoric acid concentration, 0.715 M; phosphoric acid concentration, 5 M; temperature, 50 °C. Those for preparing the material with uniform crystal-size distribution and a possibly large-mean crystal size were: ZrOCl2·8H2O, 0.13 M; hydrofluoric acid concentration, 0.715 M; phosphoric acid concentration, 9 M; temperature, 60 °C. The product was confirmed to be crystalline Zr(HPO4)2·H2O by means of chemical, thermal, and X-ray analyses, and by an examination of the titration curve.