Effect of La-doping on the properties of CaCu3Ti4O12 dielectric ceramics

Nano-size Ca1−χLa2χ/3Cu3Ti4O12 (χ = 0.00, 0.05, 0.10, 0.15 and 0.20) precursor powders were prepared via the sol–gel method and the citrate auto-ignition route and then processed into micro-crystal Ca1−χLa2χ/3Cu3Ti4O12 ceramics under heat treatment. Characterization of the as-obtained ceramics with XRD and SEM showed an average grain sizes of ∼1–2 μm, indicating La3+ amount to have little impact on grain size. The room-temperature dielectric constant of the Ca1−χLa2χ/3Cu3Ti4O12 ceramics sintered at 1000 °C was of the order of 103–104 despite the variation of χ values. Compared with CaCu3Ti4O12, La3+-doped CaCu3Ti4O12 showed a flatter dielectric constant curve related to frequency. It was found that the loss tangent of the Ca1−χLa2χ/3Cu3Ti4O12 ceramics was less than 0.20 in ∼600–105 Hz region, which rapidly decreased to a minimum value of 0.03 by La3+doping with χ = 0.05. Our measurement of the ceramics conductivities (σ) also indicated that the appropriate introduction of La3+ into CaCu3Ti4O12 would distinctly result in its dielectric properties.