The Investigation On Preparing And B-site Doping Of The High Dielectric Material CaCu₃Ti₄O₁2

In this work, the Pechini method was used to prepare the single-phase CaCu3Ti4O12 (CCTO) materials, and the effect of this method on the dielectric properties were investigated. The influence of Zr doping and FeNb codoping on the dielectric properties of CCTO material were also researched, respectively.The experimental result shows that it is successful to prepare the single-phase CCTO powder using the Pechini method. Compared with the solid-state reaction method, the reaction temperature is lower and the reaction time is also shorter. The dielectric constant of the samples preparing by the Pechini method is more than that by solid-state reaction method one times, and the loss is lower than the latter. The impedance spectroscopy of samples shows that the resistivity of grain boundary is increased using the Pechini method and the one of grain is decreased.CaCu3(Ti1-xZrx)4O12 (x=0,0.01,0.02,0.03) powders are successfully obtained by Pechini method. The low frequency (f≤105 Hz) dielectric constant decreases with the addition of Zr and the high frequency (f≥10’Hz) dielectric constant is unchanged. The low-frequency relaxation was observed at room temperature in Zr-doped samples. A corresponding equivalent circuit was adopted to analyze these effects. The characteristic frequency of low-frequency relaxation rises due to the decrease of the resistivity of grain boundary with the addition of Zr, which is likely responsible for the large low-frequency response at room temperature.FeNb-codoped CCTO materials CaCu3(Ti1-xFex/2Nbx/2)4O12(x=0.06,0.1,0.2,0.5) are prepared through solid-state reaction method. The effects on dielectric properties of CCTO are different with the FeNb-codoping level. At the frequency of 1KHz, the dielectric constant is decreased with the doping level of 6% and 10%, however, the loss is increased; For 20% and 50% doping level samples, both of dielectric constant and loss are increased. Compared with pure CCTO, the independence of the frequency is reduced with the addition of FeNb. From the impedance spectroscopy of samples, we found the resistivity of grain boundary is reduced and the one of grain is enhanced with FeNb-doping. Consequently, the characteristic frequency of the low-frequency relaxation is enhanced and the one of the high-frequency relaxation is reduced, which is likely responsible for the low independence of the frequency.