Flux Crystal Growth of Potassium Lanthanide Double Vanadates With Lanthanide-Dependent Coordination Number Variance

A series of potassium rare earth double vanadates is presented. Single crystals of double vanadates with stoichiometry K3Ln(VO4)2 (Ln = La, Pr, Nd, and Sm) and crystallizing in the glaserite structure type were synthesized via a molten alkali chloride/fluoride flux reaction. Different structures were observed depending on the constituent rare earth: K3La(VO4)2 crystallizes in an as-of-yet unreported modification of the typical glaserite structure in the space group P21/c, likely due to its larger ionic size that results in an increase in the lanthanide coordination number (seven to eight). The Pr, Nd, and Sm compositions are isostructural with their phosphate analogues and crystallize in the space group P21/m. A discussion of the synthetic details, structure determination, structure descriptions, and coordination number variance is presented.