Effect of additives on the microstructure and thermal properties of a mica-based glass-ceramic

✍ Scribed by Denry, I. L. ;Holloway, J. A.

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 411 KB
• Volume: 63
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/jbm.10122

✦ Synopsis

Abstract

Previous work has shown that lithium mica glass‐ceramics were excellent potential candidates as dental ceramics. The purpose of this study was to evaluate the effect of various additives on the microstructure and thermal properties of a mica glass‐ceramic in the system Li~2~O‐K~2~O‐SiO~2~‐MgO‐F. Five glass compositions were prepared: a base composition and four compositions with various additives. The compositions were melted at 1400 °C for 2 h and cast into 50 × 8 mm ingots. Differential thermal analyses were performed on the glasses up to 1400 °C. Bars (4 × 8 × 25 mm) were cut from the ingots and heat treated at various temperatures. The crystalline phases were analyzed by x‐ray diffraction. The microstructure was investigated by scanning electron microscopy. The percent crystallinity, crystal density, and average particle size were calculated from stereology measurements. X‐ray diffraction revealed that the major crystalline phase was taeniolite for all glass‐ceramics. Differential thermal analyses showed that the crystallization exotherm occurred in the temperature range 600–700 °C. The addition of calcium fluoride was most efficient in promoting the growth of mica crystals. Larger mica plate diameter could be beneficial to the crack‐propagation resistance of the glass‐ceramic. The addition of aluminum phosphate promoted nucleation rather than crystal growth and led to a significantly lower glass transition temperature and crystallization exotherm temperature. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 146–151, 2002; DOI 10.1002/jbm.10122