Microwave dielectric properties of low-temperature sintered Li3AlB2O6 ceramic

The Li3AlB2O6 ceramic were prepared by using the conventional solid-state reaction method; these pellets were sintered at the temperature range of 650–775 °C for 2 h in air. The X-ray powder diffraction pattern of the Li3AlB2O6 ceramic sintered at 650 °C showed a single phase which corresponded to the triclinic phase with a space group of P 1 ¯ ; the crystallization of the ceramics was observed with increasing the sintering temperatures from 650 to 775 °C. The dielectric constant of the Li3AlB2O6 ceramic increased slightly from 4.2 to 5.4 as the sintering temperatures were increased from 650 to 775 °C, whereas the Q × f value of the ceramic ranged from 12,460 to 20,448 GHz. The improvement in the Q × f value is substantially related to the crystallization of the Li3AlB2O6 ceramic. The temperature coefficient of resonant frequency of the ceramic showed the large negative values, ranging from −290 to −201 ppm/ °C. However, by the addition of 5 wt% TiB compound, the τf value of the Li3AlB2O6 ceramic was improved (τf ≒ 10 ppm/ °C); a dielectric constant of 4.2 and Q × f value of 13,027 GHz were obtained at the sintering temperature of 675 °C.