Anhydrous Lanthanide and Actinide(III) and (IV) Orthophosphates Mem(PO4)n. Synthesis, Crystallization, Structure, and Properties

Abstract

Anhydrous orthophosphates Mem(PO4)n, where Me is an element in the oxidation state +1 (A), +2 (B), +3 (R), +4 (M), or +5 (C), containing f elements(III) and (IV), are systematized. Their crystallographic characteristics are described, and the common and specific features of structure formation are discussed. The main structural (mineral) types realized in lanthanide and actinide phosphates are revealed: eulytite, zircon, monazite, NaZr2(PO4)3 (NZP), NaTh2(PO4)3 (NThP), rhabdophane, Sb0.5Bi1.5(PO4)3 (SbBi), whitlockite, arcanite, glaserite, langbeinite, scheelite, Sc2(WO4)3 (ScW). The crystal-chemical factors determining the stability of structures, polymorphism of cations, morphotropy in the series, and possibility of formation of solid solutions on the basis of iso- and heterovalent isomorphism and isodimorphism are analyzed. The possibility of predicting new compounds of f elements of the expected structure is demonstrated.