Effects of La ₂ O ₃ on Crystallization, Microstructure, and Properties of MgO‐Al ₂ O ₃ ‐SiO ₂ ‐TiO ₂ ‐La ₂ O ₃ Glass–ceramics

A new glass–ceramic material with dielectric constant ε _r ~10–11 and optimum quality factor Q × f ~22,900 GH z was fabricated from 1MgO‐1.2Al ₂ O ₃ ‐2.8SiO ₂ ‐1.2TiO ₂ ‐ xL a 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 GH z to 22,900 GH z. 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.