MgTiO3–Ca1−xSm2x/3TiO3 (x = 0.2–0.5) microwave dielectric composites with greatly improved temperature stability

Abstract

AbstractMgTiO3–CaTiO3 composite is one of the most important commercial microwave dielectric ceramics. However, the significant nonlinear change in resonant frequency with temperature and the temperature dependence of its temperature coefficient of resonant frequency (τf) severely deteriorate the temperature stability of MgTiO3–CaTiO3 composite. In this study, the Ca2+ in CaTiO3 was partially substituted with Sm3+ to prepare a series of (1 − y)MgTiO3–yCa1−xSm2x/3TiO3 (x = 0.2–0.5) composites that was subsequently characterized. With increasing x from 0 to 0.5, the y value for obtaining the near‐zero average τf between 20 and 80°C increases from 0.07 to 0.23; the dielectric constant of the composite correspondingly increases from 21.5 to 27.1, whereas the Qf value first increases and then decreases. Notably, (1 − y)MgTiO3–yCa1−xSm2x/3TiO3 composites with greatly improved temperature stability are realized, and the nonlinearity of the change in resonant frequency with temperature and the rate of change of τf with temperature are reduced by 48%–73%, relative to those of 0.93MgTiO3–0.07CaTiO3 composite. These results are attributed to the significantly reduced temperature dependence of τf for the constituent phase of Ca1−xSm2x/3TiO3. This study sheds light on the development of temperature‐stable microwave dielectric composites featuring constituent phases with τf of opposite signs.