Alkaline Phlogopite Glass-Ceramics

The complexity of this system clearly shows that a simple comparison with the ternary system Si02-Al203-Mg0 would not provide accurate information regarding the glass formation potential of the above system and crystal phase formation, since the ternary system has been completely changed and expanded by the numerous additions. 

The desired main crystal phase of the phlogopite type was formed at temperatures above 850°C, entirely consuming the norbergite. Fluorborite, Mg3(B03)F3 developed as a secondary crystal phase. Optimal microstructure formation, however, occurred at 950 C. 

Fluorphlogopite is a solid solution with the following approximate formula  

The total number of anions (oxygen and fluorine ions) must equal 12. The remaining parameters were determined x = 0.01 — 0.2, y = 0.1 — 0.2, and w = 0 - 0.1. 

The microstructure of the mica glass-ceramic of the phlogopite-type demonstrates direct interlocking of the mica crystals after heat treatment at 950 C for 4 h. This morphology is described as a house-of-cards in Section 3.2.6. 

---

Hoda and Beall (1982) developed a glass-ceramic free of alkaline ions, such as Na, K", or Li. The main crystal phase was formed of alkali-free phlogopite. The investigations of Hoda and Beall (1982) concentrated on the formation of the main crystal phases of... 

---