Metal phosphate composite and dense material comprised of the same

A metal phosphate composite having a composition represented by the formula M1xM21-x(HwPyOz) (wherein M1 represents at least one element selected from the group consisting of tin, titanium, zirconium, silicon, and germanium, M2 represents an element having a valence of 3, and x, w, y, and z satisfy the following relationship, 0.5≦x<1, 0≦w, 2<y<10, and 0<z<35).

A metal phosphate composite comprising a metal phosphate having a composition represented by the formula M1xM21-xP2O7 (wherein M1 represents at least one element selected from the group consisting of tin, titanium, zirconium, silicon, and germanium, M2 represents an element having a valence of 3, and x satisfies the relationship 0.5≦x<1), a phosphoric acid represented by the formula HaPbOc (wherein 0≦a, 0<b, and 0<c), and/or a crystalline phosphate hydrate having a composition represented by the formula M1(HPO4)2·nH2O (wherein M1 represents at least one element selected from the group consisting of tin, titanium, zirconium, silicon, and germanium, and n is 1 or 2), wherein the ratio P/(M1+M2) of the number of atoms contained in the complex is larger than 2.

A metal phosphate composite prepared by mixing a phosphoric acid material, an M1-containing compound (wherein M1 represents at least one element selected from the group consisting of tin, titanium, zirconium, silicon, and germanium), and an M2-containing compound (wherein M2 represents an element having a valence of 3) so that the ratio P/(M1+M2) of the number of atoms is larger than 2, and heating the mixture at a predetermined temperature.