Study On Microstructures And Properties Of XSrTiO₃-(1-x)La(Mg_0.5Ti_0.5)O₃ Microwave Ceramics

Microwave dielectric ceramic is a widely used functional material, which possess high dielectric constant ε_r, high quality factor Q, and small temperature coefficient of resonant frequency Ï„_f .Dielectrics are used as key materials of microwave devices in microwave communication systems,such as filters,resonances and so on. The used microwave dielectric ceramics are required to have not ony the optimal microwave dielectric properties in the high frequency range but also low prices of the materials. In this study,the microwave dielectric properties of the system composed of SrTiO₃ that exhibits a positive Ï„_f and La(Mg_0.5TiO₅)O₃ that possesses a negative Ï„_f have been investigated to obtain a new microwave dielectric ceramic, which exhibits a high ε_t, a low dielectric loss and a near-zero temperature coefficient of resonant frequency Ï„_f.The complete solid solution system was fabricated by conventional solid-state method. The microstructure of the ceramics was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD shows that the ceramics perform the complete solid solution without any other impurity but some weak peaks of supercell diffraction.SEM shows that the apparent density is very high and the porosity variously low. Microwave dielectric properties performed by HP8722ET network analyzer showed non-linear behavior for the changes of x value range from 0 to 1.0.The microwave dielectric ceramics was fabricated when x=0.4 in the xSrTiO₃-(l-x)La(Mg_1/2Ti(1/2))O₃ ceramics system. The0.4SrTiO₃-0.6La(Mg(1/2)Ti(1/2))O₃ ceramic sintered at 1550℃ exhibited the optimal dielectric properties: ε_r=46.5, Q×f=17600GHz, 且 Ï„_f =1.3 ppm/℃.In this research work, Effect of V₂O₅ additive to 0.4SrTiO₃-0.6La(Mg_1.5Ti(0.5))O₃ ceramics on sintering behavior and microwave dielectric properties had been investigated. According tothese research, the addition to ceramics could increase the dielectric loss but decrease the sintering temperature variously. When sintered at 1400°C, the 0.4SrTi03-0.6La(Mgo.5Tio.5)03 ceramics doped with 0.25% V2O5 showed the optimal microwave dielectric properties: ï¿¡,.=50.7, Qx/ = 15049.6GHz, ry=-1.7ppm/°C.