Study On The Doping Modification Based On The BLTN Microwave Dielectric Ceramics

With the development of the microwave communication technology,microwave dielectric ceramics are the key materials applied in the microwave components such as the dielectric resonator and the microwave filter.The microwave dielectric ceramics with great properties have widely attracted attentions and researches.The Ba₃La₂Ti₂Nb₂O₁₅?BLTN?microwave dielectric ceramics were prepared by solid state reaction method in this paper.The preparation processing?microstructure and microwave dielectric properties of the BLTN ceramics were investigated.The ways of the ion substitution and the doping modification have been explored to improve the microwave dielectric properties of BLTN ceramics.The effects of the processing parameters for example the pre-sintering temperature?milling time and sintering temperature on the BLTN ceramics'microwave dielectric properties have been investigated.By the comparison of the powder particle size distribution and the BLTN microwave dielectric properties,the results can confirm that the raw powders pre-sintering temperature is in 1200?.And the profitable milling time eventually is 6h by testing the particle sizes after different milling time.Next further researches on the BLTN ceramics sintering temperature showed that 1440?is the best sintering temperature by investigating the microstructure and the microwave dielectric properties.The relationship between the microstructure and the property have been investigated by the substitution of Nd³⁺for La³⁺at A-site and Ta⁵⁺for Nb⁵⁺at B-site.As for Ba₃La_2-xNd_xTi₂Nb₂O₁₅,when the x is more than 0.4,the transition of the orthorhombic perovskite structure in the BLTN ceramics caused the permittivity increases from 48 to 62?the quality factor decreases sharply and the?_f moves to negative tendency from 3.6 ppm/?to-20 ppm/?.As for Ba₃La₂Ti₂Nb_2-xTa_xO₁₅,when the x=1,due to the high melting point of Ta₂O₅,the BLTN ceramics can't be sintered compactly in 1460?.When x=0.2%,the optimal microwave dielectric properties was obtained:?_r=50.3,Q×f=12400GHz?5.07GHz?,?_f=-1.8ppm/??In order to increase the BLTN microwave dielectric property and reduce the sintering temperature,the low-melting-point oxide for example ZnO?Bi₂O₃?CuO and CaCO₃ were added into the BLTN ceramics.When the doping amount is 0.2%,the BLTN ceramics obtained the better microwave dielectric properties which were exacerbated with the doping amount rising.When the Bi₂O₃ doping amount x=0.2%,the optimal microwave dielectric properties was obtained,?_r=53.4,Q×f=13500GHz?4.71GHz?,?_f=-2.0ppm/?.