Crystal Structures and Microwave Dielectric Properties of (Ba_(1-x)Sr_x)La_4Ti_4O_(15)(x=0.8-0.95) Ceramics

The(Ba1-xSrx)La4Ti4O15(x=0.8 0.95) ceramics were prepared by the solid-state reaction method and the phase compositions,crystal structures and microwave dielectric properties were investigated.The results show that the(Ba1-xSrx)La4Ti4O15ceramics have the main phase of SrLa4Ti4O15and the second phase of SrLa8Ti9O15.The SEM images indicate that the Ba0.2Sr0.8La4Ti4O15ceramic with dense microstructures has grain sizes of about 10 20 μm and clear crystal boundaries.The grain shapes of the(Ba1-xSrx)La4Ti4O15 ceramics change with increasing x values,and the pores in the samples increase.(Ba1-xSrx)La4Ti4O15 ceramics with x=0.8 possesses excellent microwave dielectric properties,listed as follows,the dielectric constant er =40.86,the quality factor Q×f≈62806 GHz,and the temperature coefficient of resonant frequency τf = 20×10 6/℃.The monotone increases of the dielectric constant er and the quality factor Q×f of the ceramics with increasing Ba2+ contents,mean that the proper substitution of Ba2+ for Sr2+ can improve microwave dielectric properties of the(Ba1-xSrx)La4Ti4O15ceramics.