Microwave Dielectric Properties of Ca0.8Sr0.2TiO3–Li0.5Sm0.5TiO3 Ceramics with Near-Zero Temperature Coefficient of Resonant Frequency

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The structural evolution and microwave dielectric properties of ($1-x$)Ca0.8Sr0.2TiO3–$x$Li0.5Sm0.5TiO3 ($x=0--1.0$) solid solutions were investigated. Most samples exhibit the single orthorhombic perovskite structure and a homogeneous microstructure with high density except for the composition with $x=0.5$ which included a small amount of the TiO2 phase. Increasing Li0.5Sm0.5TiO3 content results in a structural change in symmetry around $x=0.8$. A-site ordering structures were observed in compositions with $x\geq 0.80$. The dielectric constant ($\varepsilon_{\text{r}}$) decreased with increasing $x$. The quality factor ($Q\times f$) decreased first up to $x=0.5$ with increasing $x$, then increased again up to $x=0.82$, and then decreased as $x$ increased to $x=1.0$. The temperature coefficient of the resonant frequency ($\tau_{\text{f}}$) decreased from high positive values to negative values with increasing $x$. A near zero $\tau_{\text{f}}$ was achieved at $x=0.81$. Optimized microwave dielectric properties were estimated to be $\varepsilon_{\text{r}}=95$, $Q\times f=3303$ GHz, and $\tau_{\text{f}}=-1.8$ ppm/°C at $x=0.81$.
2008-09-25