Optimization of dielectric properties of barium rare earth titanate by complex substitution

摘要

The optimization of dielectric properties of barium rare earth titanate was carried out by simultaneous substitution of Sm, La and Bi ions. The effects of substitution of Bi on dielectric and structural characteristics of Ba_4(La_(0.3)Sm_(0.7))_(9.33)Ti_(18)O_(54) were investigated. The solid solutions, Ba_4(La_(1-y-z)Sm_yBi_z)_(9.33)Ti_(18)O_(54) with y = 0.7 and z = 0.0-0.2, synthesized by solid state reaction technique were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The dielectric properties were measured using a network analyzer in the frequency range 0.3-3.0 GHz. It has been found that Bi substitution not only increases the dielectric constant but also improves the temperature coefficient of resonant frequency. However the tangent loss increases with increase in Bi substitution. Among the investigated compositions, Ba_4(La_(1-y-z)Sm_yBi_z)_(9.33)Ti_(18)O_(54) dielectric ceramic with y = 0.7 and z = 1.0 has got high dielectric constant (82), low tangent loss (3.3 X 10~(-3)) at 3 GHz and near zero temperature coefficient of resonant frequency (—5 ppm/°C). It could be suitable candidate for applications in wireless communication systems.