Abstract
Crystal-chemical approach provided the scientific basis for the design of new compounds with desirable structure and properties. We systemized our and literature data on the synthesis, structures and physicochemical characteristics of complex anhydrous phosphates formed by cations in oxidation degrees ranging from +1 to +4 (M+ - Li, Na, K, Rb, Cs; M2+ - Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn; M3+ - Fe, M4+ - Ti, Zr, Hf), including phosphates in which PO4 has been partially replaced by TO4 (T = Si, As, V, Mo, S). To study the influence of M+ and M4+, M2+ and M4+ radii on the stability regions of different structural types, we studied the phase formation in the M+1-xM’+ M4+4/3(PO4)3, M+Zr2(TO4)x(PO4)3-x, M2+0.5+xM’2+xM4+2-x(PO4)3, Ba3/2Fe2(PO4)3, M+M2+MgM4+(PO4)3, M+ 5/3MgM4+(PO4)3 and M2+0.5(1+x)FexTi2-x(PO4)3 systems with smoothly varying compositions. The key factors responsible for the formation of a particular type of structure are analyzed. The possibilities are considered for preparing structures of a desired type and for fine tuning of properties of obtained ceramics by varying the cationic and anionic components of the phosphate with retention of stable structural fragments of the crystal ensemble.
