Investigation of the systems KAlF4–KBe2F5 and K3AlF6–KBe2F5

Phase relations in the systems KAlF4–KBe2F5 and K3AlF6–KBe2F5 have been investigated by DTA and XRD methods. The KAlF4–KBe2F5 is a simple eutectic system with the eutectic point at a composition of 80.0 mol% KBe2F5 at 335°C. For the later system, two incongruent compounds 2K3AlF6·KBe2F5 and K3AlF6·KBe2F5 melting at 448 and 378°C, respectively were confirmed. They have been XRD indexed as both orthorhombic cells with cell parameters a=10.70±0.01, b=10.36±0.01, c=5.85±0.02 Å for the former and a=10.499±0.003, b=9.685±0.005, c=7.554±0.005 Å for the later. One eutectic point located at 85.0 mol% KBe2F5 at 336°C was also observed.