Phase formation in the InPO4-Na3PO4-Li3PO4 ternary system

The 950°C isothermal section of the InPO 4 -Na 3 PO 4 -Li 3 PO 4 ternary system was studied and constructed; one-, two, and three-phase fields are outlined. Five solid-solution regions exist in the system: solid solutions based on the complex phosphate LiNa 5 (PO 4 ) 2 (olympite structure), the indium ion stabilized high-temperature Na 3 PO 4 phase (Na 3(1 − x ) In x (PO 4 ); space group Fm m ), the complex phosphate Na 3 In 2 (PO 4 ) 3 , and the α and β phases of the compound Li 3 In 2 (PO 4 ) 3 . A narrow region of melt was found in the vicinity of eutectic equilibria. All the phases detected in the system are derivatives of phases existing in the binary subsystems. Isovalent substitution of lithium for sodium in Na 3 In 2 (PO 4 ) 3 leads to a significant increase in the region of a NASICON-like solid solution.