Investigation of dielectric properties and microstructure of sintered 13·2Li2O − 67·6SiO2 − 14.49Al2O3 − 3·3TiO2 − 0.4BaO − 0.97ZnO glass-ceramics

Lithium aluminosilicate (LAS) is an interesting material for the electronics industry. The material has near zero water absorption, low dielectric constant, and low loss tangent. Therefore, this material is interesting for the packaging of radio frequency transmitters used under harsh conditions. In this study, LAS glass powders with different particle sizes were dry pressed. Densification, crystallization, microstructure and dielectric properties were studied during thermal treatments. The highest sintered density (about 97%) has been achieved with milled powder with a d90 of about 6 μm. Investigation of the microstructure reveals that flaky rutile has formed in β-spodumene grain boundaries even though spherical rutile is observed inside of β-spodumene. Glass phase in grain boundaries contain mostly SiO2, Al2O3 and ZnO. Impedance analysis showed that the dielectric constant is influenced by phase transformation and density. The formation of hexagonal LiAlSi2O6 increases the dielectric constant while transformation to tetragonal structure decreases the dielectric constant.