TEMPERATURE-DEPENDENCE OF INTERSITE DISTRIBUTION OF ZN AND MG IN GAMMA-(ZN, MG)-ORTHOPHOSPHATES

The temperature dependence of the Zn2+/Mg2+ cation ordering among five - and six-coordinated metal sites in gamma-(Zn1-xMgx)(3)(PO4)(2) solid solutions has been studied by X-ray powder diffraction methods. The s tructures of polycrystalline samples (P2(1)/n; Z = 2) prepared at and quenched from different temperatures have been refined with the Rietve ld technique. The structure factor R-values are in the range 0.04-0.05 . It is shown that ordering with zinc preferably at the five-coordinat ed site is enhanced with temperature. Approximate thermodynamic data f or the exchange reaction have been derived.