Mixture Behavior and Microwave Dielectric Properties in the Low-fired TiO₂–CuO System

The mixture behavior and microwave dielectric properties of TiO 2 doped with CuO sintered at around 900°C for 2 h were investigated using X-ray powder diffraction and a network analyzer. Low-fired TiO 2 with 2% CuO had a quality factor of 14000, relative dielectric constant ( ε r ) of 98, and a temperature coefficient of resonant frequency (τ f ) of 374 ppm/°C. The microwave dielectric properties of low-fired, CuO doped TiO 2 could be interpreted by observing the dielectric properties of CuO: high loss tangent (tan δ), low dielectric constant, and a negative temperature coefficient of resonant frequency. The microwave dielectric properties of low-fired, CuO doped TiO 2 showed a dependence on the mixture formation of TiO 2 and CuO. More importantly, the ε r of low-fired TiO 2 with CuO could be predicted by the logarithmic mixing model. Therefore, the variation of the microwave dielectric properties was attributed to the mixture behavior of TiO 2 and CuO.