CRYSTAL-GROWTH AND CRYSTAL-STRUCTURE OF KTB(CRO4)2

Single crystals of TbK(CrO4)2 were grown hydrothermally from a mixture K2Cr2O7 and Tb2O3 (molar ratio 10:1) at 127°C. They are orthorhombic,P212121, witha = 13.804(5), b = 5.735(1), c = 9.029(3)Å,Z = 4.The structure, different to the one observed for other members of the seriesLnK(CrO4)2(Ln =La, Eu),consists of CrO4 tetrahedra (mean Cr{single bond}O distance 1.66A °) and TbO8 bicapped trigonal prisms (mean Tb{single bond}O distance 2.40A °) sharing corners and forming large channels parallel to thebaxis, where the K atoms are located. The structure can also be described as a distorted CsCl-like arrangement where Tb and K atoms occupy alternate positions of the Cs substructure. The compound could be formulated as (Tb,K)(CrO4). © 1990 Academic Press, Inc. All rights reserved.