Synthesis of phabdophane [(Ce sub(1-x), Y sub(x))PO4.nH2O(n=0.5 - 1)] and its thermal change

Rhabdophane [hexagonal form (Ce sub(1-x), Y sub(x))PO4.nH2O(n = 0.5 -- 1] was synthesized by precipitation from the mixed solution of CeCl3, YCl3 and H3PO4 (or orthophosphate) above 200C. The amount of substitution of Y for Ce was in the range 0 <= x < 0.22. Crystalline rhabdophane was detected in the precipitate obtained from the mixed solution at pH 1 -- 3. The minute crystals showed needle-like shape. Amorphous precipitate was obtained at higher pH than 3. At the pH below 1, precipitation was not proceeded at 200C. Rhabdophane was found to have zeolitic water. The amount of water increased from n = 0.5 to 1 with increasing Y contents. The zeolitic water was dehydrated in the temperature range 190 -- 2250C in air. Anhydrous (Ce sub(1-x), Y sub(x))PO4 transformed from a hexagonal into a monoclinic form at above 5000C. This transformation was monotropic and sluggish. The monoclinic form (Ce sub(1-x), Y sub(x))PO4 was the same as the mineral monazite. (author)