New microwave dielectric system of Li4xMg3(1−x)Al6(1−x)Ti5xO12 with adjustable thermal stability and high quality factor

Li4xMg3(1−x)Al6(1−x)Ti5xO12 (x = 0.2, 0.4, 0.6, 0.8) ceramics were prepared by a solid state reaction method. The phase evolution, microstructure and composition of ceramics were investigated using X-ray powder diffractometer, scanning electron microscope, energy dispersive spectrometer. The microwave dielectric properties of ceramics were studied by a network analyzer. Both MgAl2O4 and Li4Ti5O12 have a cubic spinel structure, whereas no uniform solid solution was formed in Li4xMg3(1−x)Al6(1−x)Ti5xO12 ceramics. There were Al-rich compounds and Ti-rich compounds in the mixed phases. With increasing x form 0.2 to 0.8, Al-rich compounds decreased and Ti-rich compounds increased. A complex phase evolution was appeared in the process, such as Mg2TiO4, Li2MgTi3O8 and Li4Ti5O12 compounds. With increasing x values, the sintering temperature was reduced from 1280 to 925 °C. Li4xMg3(1−x)Al6(1−x)Ti5xO12 ceramics presented an excellent comprehensive performance with εr of 11.5–26.5, Q × f values of 7102–30,191 GHz and τf values of −55.4 ~ +5.7 ppm/ °C.