Effect of additives on the microstructure and thermal properties of a mica-based glass-ceramic.
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 x 8 mm ingots. Differential thermal analyses were performed on the glasses up to 1400 C. Bars (4 x 8 x 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.
Denry
I L
IL
Section of Restorative Dentistry, Prosthodontics, and Endodontics, College of Dentistry, The Ohio State University, Columbus, Ohio 43218, USA. denry.1@osu.edu
Holloway
J A
JA
D017607:Aluminum Compounds / Q000737:chemistry / Q000494:pharmacology; D000538:Aluminum Silicates; D002124:Calcium Fluoride / Q000737:chemistry / Q000494:pharmacology; D002516:Ceramics / Q000737:chemistry* / Q000592:standards; D003460:Crystallization; D003801:Dental Veneers / Q000592:standards*; D004055:Differential Thermal Analysis; D005898:Glass; D008094:Lithium; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry / Q000494:pharmacology; D014961:X-Ray Diffraction
D017607:Aluminum Compounds; D000538:Aluminum Silicates; D010710:Phosphates; D008094:Lithium; C012714:aluminum phosphate; D002124:Calcium Fluoride; C011934:mica