Wide thermal expansion in Ag0/Au0 nanoparticle doped SiO2-MgO-Al2O3-B2O3-K2O-MgF2 glass-ceramics

Abstract

This report demonstrates high temperature sealing tendency of alumino-silicate glasses (ASG) on the system SiO2-MgO-Al2O3-B2O3-K2O-MgF2 doped with silver (Ag) and gold (Au) nanoparticles. Density of the melt-quenched (1550 °C) glasses were in 2.51–2.55 g.cm−3. The glasses were heat-treated at 900 ± 10 °C over which the opaque glass-ceramics were obtained with major crystalline phase (XRD) fluorophlogopite mica [KMg3(AlSi3O10)F2] with secondary phase norbergite (Mg2SiO4.MgF2). FESEM study indicated the development of Rod-like and rock-like crystallite particles (size ∼1–4 µm) randomly dispersed in mother glass–ceramic which was restructured into nanocrystalline morphology (crystallite size ∼100–400 nm) with the aid of Ag- or Au- nanoparticles. The significant change in microstructure influenced the corresponding density (2.51–2.55 g.cm−3) and thermal expansion characteristics. Coefficient of thermal expansion (CTE) for ASG was estimated to be 9.96 ± 0.10×10−6/K (50–800 °C), which increased to 10.46–11.01×10−6/K when doped with Ag- or Au- content. Such wide CTE (11.01 ± 0.11×10−6/K) value matches well with the CTE of ceramic/metallic materials used for high temperature application thus Ag- doped SiO2-MgO-Al2O3-B2O3-K2O-MgF2 glass can be a suitable for high temperature sealing application (like SOFC).