Effect of strontium-to-calcium ratio on the structure, crystallization behavior and functional properties of diopside-based glasses

Abstract

The role of Sr/Ca ratio, which was varied from 3/6 to 9/0, on the structure, crystallization behavior and properties of diopside-based glass and glass-ceramic sealants targeted to solid oxide fuel cell (SOFC) applications was evaluated. The structural changes undergone by glass-powder compacts during isothermal heat treatment at 850 degrees C for 1-1000 h were investigated using XRD (X-ray diffraction) analysis, including quantitative Rietveld refinement, and MAS-NMR (magic angle spinning nuclear magnetic resonance) techniques. The tendency towards crystallization was retarded with increasing Sr/Ca ratio. Diopside-based phases, strontium akermanite and magnesium silicate were developed under various heat-treatment conditions. MAS-NMR analysis of glasses heat treated for 1000 h revealed that with increasing Sr/Ca ratio, Q(1) and Q(4) structural units were formed at the expenses of Q(2) units. The good thermal stability and chemical compatibility of the new glass-ceramic compositions coupled with their mechanical reliability and high electrical resistivity make them attractive for further experimentation as sealants for SOFCs. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.