MgTiO ₃ –Ca _{1− x} Sm _{2 x /3} TiO ₃ ( x = 0.2–0.5) microwave dielectric composites with greatly improved temperature stability

Abstract MgTiO 3 –CaTiO 3 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 ( τ f ) severely deteriorate the temperature stability of MgTiO 3 –CaTiO 3 composite. In this study, the Ca 2+ in CaTiO 3 was partially substituted with Sm 3+ to prepare a series of (1 − y )MgTiO 3 – y Ca 1− x Sm 2 x /3 TiO 3 ( 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 τ f 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 )MgTiO 3 – y Ca 1− x Sm 2 x /3 TiO 3 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 τ f with temperature are reduced by 48%–73%, relative to those of 0.93MgTiO 3 –0.07CaTiO 3 composite. These results are attributed to the significantly reduced temperature dependence of τ f for the constituent phase of Ca 1− x Sm 2 x /3 TiO 3 . This study sheds light on the development of temperature‐stable microwave dielectric composites featuring constituent phases with τ f of opposite signs.