CSPR(CO3)2 - 1ST SINGLE-CRYSTALS OF AN ANHYDROUS TERNARY RARE-EARTH CARBONATE

For the first time, single crystals of CsPr(CO3)2 were obtained by thermolysis of Cs2(H3O)Pr(CH3COO)6 at 400-degrees-C under high CO2 pressure (300 bar) in a steel autoclave. The crystal structure (triclinic, P1BAR, Z = 4, a = 860.2(3), b = 887.4(3), c = 892.6(3) pm, alpha = 98.56(2), beta = 96.19(1), gamma = 115.29(2)-degrees, V(m) = 90.03(6) CM3 /mol, R = 0.033, R(w) = 0.029) was determined from four-circle-diffractometer data. CsPr(CO3)2 forms an aragonite like layer structure. Layers containing (Cs+ and Pr3+ in a 1 : 1 ratio are stacked in the fashion of the hexagonal closest packing in the [001] direction. They are separated through CO32- ion layers. The Pr3+ ions are surrounded by 8 or 9 oxygen atoms, the coordination numbers of Cs+ are 11 and 12. The site symmetry of the CO32-ions is C1. All bands of the internal vibrations are observed in the IR spectrum. CsPr(CO3)2 decomposes above in 435-degrees-C to Cs2CO3 and Pr2O2CO3.