Effects of La₂O₃ on Crystallization, Microstructure, and Properties of MgO‐Al₂O₃‐SiO₂‐TiO₂‐La₂O₃ Glass–ceramics

Abstract

A new glass-ceramic material with dielectric constant e r~1 0-11 and optimum quality factor Q 9 f~22,900 GHz was fabricated from 1MgO-1.2Al 2 O 3 -2.8SiO 2 -1.2TiO 2 -xLa 2 O 3 (x = 0.1, 0.2, 0.3, and 0.4) system, and the effects of La 2 O 3 on crystallization, microstructure, and dielectric properties of the material were investigated. The results show that the main crystalline phases in the glass-ceramics are lanthana-based perrierite, rutile, and cordierite. As the content of La 2 O 3 increases, the formation of perrierite is promoted, while that for rutile and cordierite is suppressed. Meanwhile, a gradual homogenization in the microstructure has been observed. Specifically, the interconnected network, the formation of which is mainly due to the aggregation of perrierite, disintegrates with the increase of x from 0.1 to 0.3 and is hardly seen when x = 0.4, finally resulting in a homogeneous microstructure with an overall uniform distribution of the phases and crystalline size. With higher content of La 2 O 3 , the dielectric constant of the material goes up slightly from 10 to 11, while the quality factor rises significantly from 12,500 GHz to 22,900 GHz. The variations of the dielectric properties are believed to be appreciably associated with the relative content of the phases present and the more homogeneous microstructure. *