Investigation of ($1-x$)(Mg0.6Zn0.4)0.95Co0.05TiO3–$x$SrTiO3 Microwave Dielectrics

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The microwave dielectric properties and microstructures of ($1-x$)(Mg0.6Zn0.4)0.95Co0.05TiO3–$x$SrTiO3 ceramics were investigated using a network analyzer and scanning electron microscope (SEM). In order to achieve a temperature-stable material, we used a method of combining a positive-temperature-coefficient material with a negative one. SrTiO3 has a large positive temperature coefficient of resonant frequency ($\tau_{\text{f}}$) of 1,700 ppm/°C. (Mg0.6Zn0.4)0.95Co0.05TiO3 possesses a negative temperature coefficient of resonant frequency of $-65$ ppm/°C. The dielectric constant and density increase with increasing SrTiO3 content. By appropriately adjusting $x$ in the ($1-x$)(Mg0.6Zn0.4)0.95Co0.05TiO3–$x$SrTiO3 ceramic system, a near-zero $\tau_{\text{f}}$ value can be obtained. A new microwave material of 0.96(Mg0.6Zn0.4)0.95Co0.05TiO3–0.04SrTiO3 exhibits excellent dielectric properties including of a dielectric constant of 23.5, a $Q \times f$ value of 92,000 GHz, and a temperature coefficient of resonant frequency of $-2.5$ ppm/°C, and can be utilized in the fabrication of microwave devices.
2009-08-25