ON RUBIDIUM LANTHANIDE DOUBLE CHROMATES

Synthesis and crystallographic data are reported for a family of double rubidiurn-rare earth chromates RbLn(CrO4)2, where Ln = La-Lu, Y and Sc. The compounds are closely related to the potassium chromates KLn(CrO4)2 but with a slightly different distribution of structural types: those of La, Pr and Nd are monoclinic, Sm, Eu, Gd are orthorhombic and those of Tb-Lu are also monoclinic but with another unit cell. RbSc(CrO4)2 has high and low temperature forms: hexagonal and monoclinic respectively. Lattice parameters of all the above compounds are given. Thermal decomposition takes place over 450-degrees-C leading to the rare earth chromites and Cr2O3.