The phase formations in the Na3PO4-InPO4 system are investigated. Forming two compounds: Na3In(PO4)2 (I) and Na3In2(PO4)3 (II) having ƒÀ(low-temperature) and a-modification (high-temperature) are determined. Their crystal structures are refined. The ƒÀ(I) and ƒ¿-(I) crystallize in the ƒÀ-K2SO4-like structure. ƒÀ-(II) an individual structure, which is different from those of ƒÀ-Na3Sc2(PO4)3. The ƒ¿-(I) crystallize in the NASICON-like structure. It is stated by the thermogravimetric analyses that the transition ƒÀ-(I)• ̈ƒ¿-(I) occurs irreversible at temperature 700•Ž and transition ƒÀ-(II) •¬ ƒ¿-(II) occurs reversible at temperature 820•Ž. INTRODUCTION The investigations of M3AO4RAO4 (M = Na, K; R = rare earth elements, Sc; A = P , V, As)1-8 binary systems has been carried out for last several years and were started because of the great interest in these compounds as new luminophore, laser materials and superionic conductors. In spite of the great interest to the Na34O4RAO4 systems, the complex compounds of indium and alkaline elements are poorly studied. The information on study of M3PO4 InPO4 (M = Li, Na) double systems is limited by synthesis description and crystallographic characteristics of some compositions.94° The information of potassiumindium complex phosphates is absent completely. The present paper reports the examinations on the Na3PO4-InPO4 double system. EXPERIMENTAL PROCEDURE The phase formation in subsolidus area of the Na3PO4-InPO4 system in whole range of component concentrations and temperature region from 600 to 950•Ž was Received October 21, 1999; Accepted November 12, 2000
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