Open AccessSynthesis and Hydrothermal Study of (Na,K)M2(PO4)3 (M = Ti, Zr, Hf) Solid Solutions
Author(s) -
Е. А. Асабина,
В. И. Петьков,
A. M. Kovalsky,
A. R. Kotelnikov
Publication year - 2010
Publication title -
eurasian chemico-technological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.227
H-Index - 9
eISSN - 2522-4867
pISSN - 1562-3920
DOI - 10.18321/ectj44
Subject(s) - solid solution , zirconium , titanium , decomposition , hydrothermal circulation , potassium , chemistry , hydrothermal synthesis , phosphate , sodium , inorganic chemistry , materials science , nuclear chemistry , chemical engineering , metallurgy , organic chemistry , engineering
(Na,K)M2(PO4)3 (M = Ti, Zr, Hf) continuous solid solutions were synthesized by sol-gel and solidstate methods. Cation-exchange reactions in the NaM2(PO4)3–KM2(PO4)3–NaCl–KCl–H2O systems were studied at T = 723 – 973 K and p = 100 – 200 MPa. The concentration dependences of unit cell parameters of the studied phosphates were found. The sodium/potassium distribution coefficients in the phosphate-fluid systems were functions of the solid solution compositions, that is, the systems behave nonideally. The excess volumes and excess Gibbs functions of solid solutions mixing were fitted to thirdorder polynomials and described in terms of the Margules model. From the comparison of the results obtained Ti-, Zr-, and Hf-systems, we made the conclusion that the titanium phosphates show greater nonideality than zirconium and hafnium phosphates and lower thermodynamic stability to decomposition to double phosphates at high pressures and temperatures.