Investigations of phase relations in the system CaONa₂OK₂OP₂O₅

Abstract

Abstract The lattice constants of the compound Ca 2 NaK(PO 4 ) 2 have been studied at room temperature using an X‐ray powder diffractometer and also in the temperature range from 20 up to 1000 °C by Guinier‐Lenné‐technology. A hexagonal lattice with the parameters a 0 = 5.4367 Å and c 0 = 7.3125 Å and a cell volume of 187.18 Å 3 has been determined for the high temperature phase, existing from 670 °C upward. At temperatures below 670 °C a superlattice structure is formed by tripling the axis a , a ′, and c so that it results in a hexagonal superlattice structure cell with the lattice constants of a 0 = 16.311 Å and c 0 = 21.939 Å and a cell volume of 5054 Å 3 .