Dielectric resonators with complex crystal structures in the La2O3-Al2O3-TiO2 system for microwave applications

LaTi2Al9O19 and La3Ti5Al15O37 ceramics in the La2O3-Al2O3-TiO2 system have been prepared by conventional solid state ceramic route. The structure and microstructure of the compositions have been studied using powder X-ray diffraction and scanning electron microscopic techniques. Laser Raman studies have been employed to understand the complex crystal structure of these compositions in molecular level. The microwave dielectric properties of the sintered ceramic compacts were measured by Hakki and Colemann post resonator and TE01 delta cavity techniques using a vector network analyzer. LaTi2Al9O19 and La3Ti5Al15O37 ceramics possess excellent microwave dielectric properties such as relatively high unloaded quality factors 7,762 and 7,415, low dielectric constant 15.7 and 22.1 and low temperature coefficient of resonant frequency values -22 and +18.9 ppm/A degrees C, respectively.