ORIGINAL ARTICLE Crystallization, mechanical, and optical properties of transparent, nanocrystalline gahnite glass-ceramics Atiar R. Molla 1,2 | Alisson M. Rodrigues 1 | Shiv Prakash Singh 1 | Ricardo Felipe Lancelotti 1 | Edgar D. Zanotto 1 | Ana C.M. Rodrigues 1 | Mohammad Reza Dousti 3,4 | Andrea S.S. de Camargo 3 | Claudio Jose Magon 3 | Igor D 0 Anci~ aes Almeida Silva 3 1 Vitreous Materials Lab (LaMaV), Departamento de Engenharia de Materiais, Universidade Federal de S~ ao Carlos, S~ ao Carlos, Brazil 2 Glass Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata, India 3 Instituto de F ısica de S~ ao Carlos- Universidade de S~ ao Paulo, S~ ao Carlos, Brazil 4 Instituto de F ısica, Universidade Federal de Alagoas, Maceio-AL, Brazil Correspondence Atiar R. Molla, Glass Division, CSIR- Central Glass and Ceramic Research Institute, Kolkata, India. Emails: atiar@cgcri.res.in, atiariitk@gmail.com Ana C.M. Rodrigues and Atiar R. Molla, Vitreous Materials Lab (LaMaV), Departamento de Engenharia de Materiais, Universidade Federal de S~ ao Carlos, Brazil. Email: acmr@ufscar.br Funding information Fundac ß~ ao de Amparo a Pesquisa do Estado de S~ ao Paulo, Grant/Award Num- ber: 2013/07793-6, 2013/09093, 2013/ 24064-8, 2014/20865-9; FAPESP (S~ ao Paulo Research Foundation), Grant/Award Number: 14/20865-9, 2013/24064-8, 2013/ 07793-6. Abstract 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 spec- troscopy. The dark brown color of the transparent precursor glass and glass-cera- mic was eliminated using CeO 2 . The increase in transparency of the CeO 2 -doped glass and glass-ceramics was demonstrated by UV-visible absorption spec- troscopy. 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, transpar- ent glass-ceramics which may be potential candidates for a variety of technologi- cal applications, such as armor and display panels. KEYWORDS glass, glass-ceramics, mechanical properties, optical materials/properties, spinels 1 | INTRODUCTION In recent times, numerous applications have been found for glass-ceramics (GCs) in both domestic and technological areas. In most cases, after the transformation from glass to glass-ceramic, the material loses optical quality, limiting some of its possible applications. For instance, the develop- ment and production of transparent colorless glass-ceramics containing important crystal phases, such as spinel, repre- sents a significant challenge because the synthesis of pre- cursor glasses, which leads to spinel glass-ceramics through crystallization, is quite difficult due to their high Received: 12 September 2016 | Accepted: 26 December 2016 DOI: 10.1111/jace.14753 J Am Ceram Soc. 2017;100:1963–1975. wileyonlinelibrary.com/journal/jace © 2017 The American Ceramic Society | 1963