The formation and structure of phases have been studied in the system of mixed-metal zirconium phosphates of alkali and tervalent elements forming formula series A(1-3x)R(x)Zr(2)(PO4)(3) (1), A(3-3x)KZr(1.5)(PO4)(3) (2), and A(5-3z)R(x)Zr(PO4)(3) (3) and described by the general formula A(m-3x)R(x)Zr(2-(m-1)/4)(PO4)(3), where A = Na or K; R = Al, Fe, or Ga; and m = 1 (0 less than or equal to x less than or equal to 0.33) in series 1, m = 3 (0 less than or equal to x less than or equal to 1) in series 2, and m = 5 (0 less than or equal to x less than or equal to 1.67) in series 3. In most cases, phosphates crystallize in the NaZr2(PO4)(3) structural type (NZP; space group R (3) over barc), except for phases Fe0.33Zr2(PO4)(3) (x = 0.33), RZr1.5(PO4)(3) (for R = Fe, Ga; x = 1), and Ga1.67Zr(PO4)(3) (X = 1.67), which are the end-members of series 1, 2, and 3, respectively. These phases have monoclinic unit cells and belong to the Sc-2(WO4)(3) structural type (SW; space group P2(1)/n). The sodium and potassium phases of the series in question have been found to differ in their phase-formation character.
