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

MgTiO3-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 (tau(f)) 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-yCa(1-x)Sm(2x/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 tau(f) between 20 and 80 degrees 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-yCa(1-x)Sm(2x/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 tau(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 tau(f) 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 tau(f) of opposite signs.

Automated summary

In this study, a series of (1 - y)MgTiO3-yCa(1-x)Sm(2x/3)TiO(3) composites with improved temperature stability were prepared by partially substituting Ca2+ in CaTiO3 with Sm3+. The results showed that with increasing Sm3+ content, the dielectric constant of the composites increased, and the nonlinearity of the change in resonant frequency with temperature and the rate of change of τ(f) with temperature decreased. This study is important for the development of temperature-stable microwave dielectric composites with constituent phases having opposite signs of τ(f).