Crystal structure of hydroxylbastnäsite-(Ce) from kamihouri, miyazaki prefecture, japan

Abstract

The crystal structure of hydroxylbastnäsite-(Ce), (Ce0.49La0.21Nd0.16Pr0.06Y0.03Sm0.02Gd0.01Th0.01Eu0.01)(CO3) (OH0.85F0.15), was solved and refined R1 = 0.0363, wR2 = 0.0871 using single crystal CCD-XRD data. The hexagonal unit cell of space group P6̄ is identical to those of synthetic RE(CO3)OH, but is different from that of bastnäsite-(Ce), P6̄2c. The refined dimensions are: a = 12.4730(9), c = 9.9607(14) å, V = 1342.0(2) å3, and Z = 18 for Ce(CO3)(OH). Each of the three crystallographically independent 9-hold RE cations is coordinated by three [(OH),F]-, four monodentate (CO3)2-, and one bidentate (CO3)2- ions in hydroxylbastnäsite-(Ce), in contrast to the 9-hold RE cation coordinated to three F- and six monodentate (CO3)2- ions in bastnäsite-(Ce). The replacement of OH for F modifies the coordination of RE polyhedra, thereby lowering the symmetry and enlarging the unit cell in the crystal structure of hydroxylbastnäsite-(Ce).