Microwave dielectric properties of (1-x)La(Mg_(0.5)Sn _(0.5))O_(3-x)(Sr_(0.8)Ca_(0.2)) _3Ti_2O_7 ceramic system with a near zero temperature coefficient of resonant frequency

摘要

In this study, the microwave dielectric properties of (1-x)La(Mg _(0.5)Sn_(0.5))O_(3-x)(Sr_(0.8)Ca _(0.2))_3Ti_2O_7 ceramic system prepared by the conventional solid-state method have been investigated for application in mobile communication. It was found that the diffraction peaks of (1-x)La(Mg_(0.5)Sn_(0.5))O_(3-x)(Sr_(0.8)Ca _(0.2))_3Ti_2O_7 ceramic system shift to higher angles as x increases from 0.2 to 0.4. It was also found that the X-ray diffraction patterns of the 0.8La(Mg_(0.5)Sn_(0.5))O _3-0.2(Sr_(0.8)Ca_(0.2))_3Ti _2O_7 ceramics exhibited no significant phase difference at different sintering temperatures. The average grain size of the (1-x)La(Mg _(0.5)Sn_(0.5))O_3-x(Sr_(0.8)Ca _(0.2))_3Ti_2O_7 ceramic system decreased from 6.4 to 4.3 μm as the value of x increased from 0.2 to 0.4 sintered at 1550 °C for 4 h. The dielectric constant increased from 26.6 to 35.9 and the quality factor (Q×f) decreased from 31,600 to 23,300 GHz for (1-x)La(Mg_(0.5)Sn_(0.5))O_3-x(Sr_(0.8)Ca _(0.2))_3Ti_2O_7 ceramic system as the x value increases from 0.2 to 0.4 sintered at 1550 °C for 4 h. The average value of temperature coefficient of resonant frequency (τ_f) increased from -18 to +8 ppm/ K as the x value increases from 0.2 to 0.4.