Deuterioxyapatite (Ca₁₀(PO₄)₆(OD)₂, DAp) was prepared from CaO, P₂O₅, and D₂O in H₂O and CO₂ free air at 298K. The obtained DAp was identified as apatite single phase by a powder XRD technique. The deuterioxyl group was found by IR and MAS-NMR techniques, but hydroxyl group was not. Further, MAS-NMR measurement suggested the DAp had no tightly-bonded OD group. The deuterioxyl group was not substituted with hydroxyl group at 298K by stirring in distilled water for 7 days. From TG-MS measurement, dried DAp powder released deuterium in two rapid steps and in a slow step up to 873K. High-temperature XRD measurement showed large thermal expansion for DAp due to lattice defect led by heating. High-temperature IR spectra showed release of deuterioxyl group without substitution by hydroxyl group above 333K. Deuterioxyl group in DAp was easily released by heating, and DAp changed into oxyapatite.

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Syntheses of rhabdophane-(Y) (hexagonal YPO₄·nH₂O (n=0.5 to 1) were carried out by precipitation from aqueous solutions of Y(NO₃)₃·6H₂O, (NH₄)2HPO₄ and citric acid with the mixing mole ratios of (NH₄)2HPO₄/Y(NO₃)₃·6H₂O=4 and citric acid/Y(NO₃)₃·6H₂O (C/Y)=5 to 30. Rhabdophane was obtained when those solutions were maintained at 90°C in the pH range 3 to 7 for 1 day to 30 days. Chemical formula and lattice constants of the well crystallized single phase rhabdophane obtained by the reaction at pH 7 and C/Y ratio 30 for 30 days were YPO₄·0.6H₂O, a=0.683 nm and c=0.630 nm, respectively. The hydrated rhabdophane was dehydrated at 180° to 250°C in air. Thereafter, no significant changes in crystal structure were seen up to 800°C. The water corresponding to 0.6H₂O was zeolitic water. Anhydrous rhabdophane gradually changed to the xenotime structure above 900°C in air.

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A small crystal fragment whose diffraction pattern shows a long period of around 138Å was found under the electron microscope, and based upon its high-resolution TEM image the essential crystal structural features were discussed. It belongs to the rathite group of lead sulfarsenites. The crystal structures of the members of this group can be interpreted as various combinations of two different structural units, namely, sartorite unit “S” with about 9.8Å in width and rathite unit “R” with about 12.6Å in width. The present material has been proved to have an ordered arrangement of RSRSR·RSRSRSR. This result is consistent with the conclusion derived by Takéuchi(1970) that the crystal structure of each member of the rathite group is constructued by a regular arrangement of S and R units. Although the 138Å period is reported for rathite-IV, the characteristics of the diffraction pattern of the present phase appear to be different from those of rathite-IV. The occurrence of the present material is discussed.

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