Crystallization behavior, densification and microwave dielectric properties of MgO-Al2O3-SiO2-TiO2 system glass-ceramics containing V2O5

Abstract

Glass-ceramics with a mass fraction composition (wt%) of 19MgO-23Al2O3-53SiO2-4TiO2-xV2O5 (x=2.5, 3 and 3.5, abbreviated as samples V2.5, V3 and V3.5) were prepared by two-step heat treatment of the parent glass at selected nucleation and crystallization temperatures for different holding time (2h and 20h), respectively. The effects of V2O5 on crystalline phases, microstructures and microwave dielectric properties of the glass-ceramics were investigated in detail. X-ray diffraction (XRD) analyses revealed that the main phases could be identified as α-cordierite and SiO2 phases, and also some amount of μ-cordierite phase and a trace of Al2Si4O10, Mg(VO4)2 and TiO2 phases were also detected in all these glass-ceramics' XRD patterns. In addition, an appropriate V2O5 addition with 3.0–3.5wt% was found to cause an increase in the content of the precipitated crystalline phases. Based on the EDM observation, a fraction of Ti4+ and V5+ ions were remained in the residual glass matrix of the crystallized specimens. Additionally, the microwave dielectric properties were closely depended on not only the different two-step heat treatment temperatures and holding time, but also the relative densities and degree of crystallization of the glass matrix. Wherein, the fully densified V3 glass-ceramic sample heat-treated at 850°C/2h+950°C/20h exhibited a lower dielectric constant (εr) of ~3.79, a higher quality factor (Q×f) of about 12,520GHz (at 13.693GHz) and a near-zero temperature coefficient of resonant frequency (τf) of ~ −5.4ppm/°C, which provided a promising candidate for LTCC applications.