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

摘要

Glass-ceramics with a mass fraction composition (wt%) of 19MgO center dot 23Al(2)O(3)-53SiO(2)center dot 4TiO(2)-xV(2)O(5) (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 (2 h and 20 h), 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 alpha-cordierite and SiO2 phases, and also some amount of-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 3.0-3.5 wt% 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 degrees C/2 h + 950 degrees C/20 h exhibited a lower dielectric constant (60 of 3.79, a higher quality factor (Q x f) of about 12,520 GHz (at 13.693 GHz) and a near-zero temperature coefficient of resonant frequency (rf) of 5.4 ppm/ degrees C, which provided a promising candidate for LTCC applications.