Study on the system Pb5Cr3F19-A(2)M(II)M(III)F(9) (A = Sr, Pb; M-II = Mg, Zn; M-III = Cr, Ga)

Solid solutions of formula Pb5-xMg2xCr3-xF19-x; Pb5-5xSr4xMg2xCr3-xF19-x an d Pb5-5xSr4xZn2xGa2xCr3-3xF19-x were found in systems Pb5Cr3F19-A(2)M(II)M( III)F(9) (A=Sr,Pb; M-II=Mg, Zn; M-III=Cr, Ga). An X-ray diffraction study a llowed characterization of a restricted single-phase domain attached to eac h end member: 0 less than or equal to x less than or equal to 0.15 and 0.8 less than or equal to x less than or equal to 1. Phase transition studies w ere carried out by differential thermal and scanning calorimetric measureme nts. The results are discussed in relationship to the nature of the cation of the host anions and compared with those obtained from A(5)M(3)F(19) fami ly (A=Sr, Pb, Ba; M=Al, Cr. Fe) and related compounds.