Synthesis of Fluorine Muscovite by Solid State Reaction Method and Its Thermal Durability

Abstract

Fluorine muscovite KAl2(AlSi3O10)F2 was synthesized through solid state reaction at 600°C for about 100h from stoichiometrical batches. Fluorine muscovite was not formed by heating these raw batches at higher temperatures above 700°C. It was indispensable for mica formation to use γ-Al2O3 as raw materials. Appropriate forming pressure for green bodies was found to be 37.5-75MPa for obtaining crystal aggregates of fluorine muscovite with well-developed interlocking house-of-cards microstructure, which gave machinability to the sintered bodies. Thermal durability of fluorine muscovite crystals in air was relatively high due to the formation of a protective vitrified phase on the surface upon decomposition. Changes in lattice constants and IR spectra suggestes the formation of fluorine muscovites having variable layer charges between 1.0-0.9.