Effect of PH on dielectric properties of CaCu3Ti4O12 ceramics by coprecipitation

CaCu₃Ti₄O₁₂ ceramics were prepared by coprecipitation method. The pH value of reaction solutions plays an important role in the coprecipitation process. First, the pH value of Ti precursor solution must be controlled at around 3, in order to get clear Ti solution. In addition, the pH value of Ca and Cu precursor solution has a great influence on the properties of both precursor and CaCu₃Ti₄O₁₂ ceramics obtained subsequently. The properties change a lot, even when the pH value of Ca and Cu solution changes in a small range. It can be seem from the XRD patterns that the content of the impurity phase increases with increasing pH value. As to the microstructure, the grain size of CaCu₃Ti₄O₁₂ ceramics decreases with increasing pH value. Most significantly, the nonlinear coefficient, dielectric constant and loss can all be adjusted by this pH value. Relatively high dielectric constant and low loss can be obtained when this pH value is 5.10. This gives us a clue to improve the properties of CaCu₃Ti₄O₁₂ ceramics which has been investigated for several years.