BAND GAP ENGINEERING OF TRANSPARENT LITHUM ALUMINOSILICATE GLASS-CERAMICS CONTAINING B-QUARTZS.S. NANOCRYSTALS

Transparent Lithium Alumino Silicate (LAS) glass-ceramics are used in advanced applications due to their high transmissibility, non-linear optical properties and near Zero thermal expansion. Because of the mentioned properties, LAS glass-ceramics are known as the precision optical instruments. Also, metastable B-quartz solid solution is considered as the desirable phase for production of transparent LAS glass-ceramics. The aim of this investigation is to study the variation in optical band gap of nanocrystalline transparent LAS glass-ceramics. According to DTA curve, the base glass was crystallized by controlling the nucleation and growth processes. The size and volume fraction of nanocrystals were calculated according to their XRD patterns. Then, it was tried to investigate thoroughly the optical band gap of samples using the UV-Vis absorption spectra. Urbach band tailing, direct and indirect optical band gaps and Fermi energy level of the specimens have been reduced by increasing of nanocrystals in glassy matrix which could be attributed to increasing of the order of the structural, destruction of recombination centers and broadening of conduction band, respectively.

Keywords:

LAS glass-ceramics , Nanocrystals , Optical band gap , Fermi level , Urbach energy