Controlled crystallization of xenotime and monazite-type crystals in glass-ceramics

摘要

Glasses derived from the chemical system of SiO2-Al2O3-CaO/SrO-Y2O3/La2O3-P2O5-F with further additives of B2O3, Na2O, K2O were formed by producing glass frits. Glass-ceramic powder compacts were produced by heat treating the glass grains in a temperature range of 800 up to 1050°C. Special glass-ceramic compositions were shown to precipitate xenotime (YPO4) and monazite-type (LaPO4) crystals in the glass matrix. The microstructure of glass-ceramics with main crystals ofmonazite and xenotime and secondary phases was analyzed by scanning electron microscopy (SEM). The glass-ceramics in question are characterized by a coefficient of thermal expansion (CTE) of 9-5 to 10.6x10~(-6) K~(-1) (100-400°C). According to biomaterials standards for dental products, these glass-ceramics show good chemical durability (in acetic acid) and translucency (measured as a contrast ratio value of 60-70).