Preparation and dielectric properties of CaCu3Ti4O12-(NaBi)0.5Cu3Ti4O12 composites

The composites of CaCu₃Ti₄O₁₂-x(NaBi)_0.5Cu₃Ti₄O₁₂, i.e. CCTO-xNBCTO, were prepared for x value from 0 to 0.1. Ultrahigh dielectric constant, ε =7×10⁵, and dielectric loss, tanδ = 0.48, of the composites with x=0.05 were obtained. The relations between crystal structures with XRD spectra and dielectric properties with LCR measurement were investigated, in which. An internal barrier layer capacitance effect is used to explain the mechanism of such dielectric behavior. The frequency dependence of the dielectric constant of CCTO-NBCTO composites were measured from 20Hz to 1MHz, showing that the loss tangent apparently decreased with the increase of frequency. The temperature dependence of both the dielectric constant and loss tangent of the samples were also obtained. It was found that the dielectric properties was almost independent of temperature in the range from -20°C to 80°C, however, the loss tangent were increased dramatically with a further increase in temperature, above 80°C.