Lanthanides in phosphates with the structure of whitlockite mineral [analog of β-Ca3(PO4)2]

Abstract

Data on phosphates with the structure of biogenic whitlockite mineral [analog of low-temperature modification of β-Ca3(PO4)2] were analyzed. The possibility of isomorphic substitution of cations in phosphates with whitlockite structure was evaluated and formation of solid solutions of various compositions involving elements in oxidations states 1+, 2+, 3+, and 4+, including lanthanides and other elements and isotopes occurring in wastes from radiochemical plants, was studied. Phosphates of Ca, Mg, and lanthanides (Sm, Eu, Gd) were prepared by the sol-gel procedure, and their thermal, thermomechanical (thermal expansion), and hydrolytic properties were determined. The results of hydrothermal and thermal experiments were compared with published data for calcium phosphate and other matrices for immobilization of radioactive wastes (RAW).