赝二元系KBe_2F_5-KAlF_4 和 KBe_2F_5-K_3AlF_6的相图研究

采用溶液反应法制备试样,用DTA和XRD方法研究了KBe2F5-KAlF4和KBe2F5-K3AlF6两个赝二元体系。结果表明:KBe2F5-KAlF4是一简单低共熔体系,共晶点组成含KBe2F580mol%,温度335℃。KBe2F5-K3AlF6体系中生成了两个中间化合物2K3AlF6·KBe2F5和K3AlF6·KBe2F5。相图中有一共晶点,组成为85mol%KBe2F5,温度336℃。2K3AlF6·KBe2F5和K3AlF6·KBe2F5都是固液异组成化合物,分别在448℃和378℃时发生分解。X-射线衍射分析证明它们均属正交晶系,晶胞参数分别为a=10.70±0.01,b=10.36±0.01,c=5.85±0.02( )和a=10.499±0.003,b=9.685±0.005,c=7.554±0.005( )。

A Study on Phase Diagram of Pseudo-binary Systems KBe2F5-KAlF4 and KBe2F5-K3AlF6

Phase relations and phase diagrams of the pseudo binary system KBe2F5 KAlF4 and KBe2F5 K3AlF6 have been studied by DTA and XRD with the samples prepared with the solution reaction method. The results indicated KBe2F5 KAlF4 is a simple low eutectic system and eutectic point is located in 80 mol% KBe2F5 at 335 ℃. Two compounds KBe2F5·2K3AlF6 and KBe2F5·K3AlF6 formed the system of KBe2F5 K3AlF6, and melted incongruently and KBe2F5·2K3AlF6 dissolved into K3AlF6 and liquidus containing 71.0 mol% KBe2F5, KBe2F5·K3AlF6 dissolved into KBe2F5·2K3AlF6 and liquidus of 79.0 mol% KBe2F5. Eutectic point that is located in 85 mol% KBe2F5 at 336 ℃ was found in KBe2F5 K3AlF6.X ray power diffraction analysis indicated that they all belong to orthorhombic with cell parameter : KBe2F5·2K3AlF6, a=10.70±0.01,b=10.36±0.01, c=5.85±0.02(); KBe2F5·K3AlF6, a=10.499±0.003, b=9.685±0.005, c=7.554±0.005(). 