Crystallization, mechanical, and optical properties of transparent, nanocrystalline gahnite glass‐ceramics

This paper describes the preparation of a transparent glass‐ceramic from the SiO 2 ‐K 2 O‐ZnO‐Al 2 O 3 ‐TiO 2 system containing a single crystalline phase, gahnite (ZnAl 2 O 4 ). TiO 2 was used as a nucleating agent for the heat‐induced precipitation of gahnite crystals of 5‐10 nm. The evolution of the ZnAl 2 O 4 spinel structure through the gradual formation of Al‐O bonds was examined by infrared spectroscopy. The dark brown color of the transparent precursor glass and glass‐ceramic was eliminated using CeO 2 . The increase in transparency of the CeO 2 ‐doped glass and glass‐ceramics was demonstrated by UV ‐visible absorption spectroscopy. EPR measurements confirmed the presence of Ce 3+ ions, indicating that CeO 2 was effective in eliminating the brown color introduced by Ti 3+ ions via oxidation to Ti +4 . The hardness of the glass‐ceramic was 30% higher than that of the as‐prepared glasses. This work offers key guidelines to produce hard, transparent glass‐ceramics which may be potential candidates for a variety of technological applications, such as armor and display panels.