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

Nano-size Ca1-chi La2 chi/3Cu3Ti4O12 (chi = 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-chi La2 chi/3Cu3Ti4O12 ceramics under heat treatment. Characterization of the as-obtained ceramics with XRD and SEM showed an average grain sizes of similar to 1-2 mu m, indicating La3+ amount to have little impact on grain size. The room-temperature dielectric constant of the Ca1-chi La2 chi/3Cu3Ti4O12 ceramics sintered at 1000 degrees C was of the order of 10(3)-10(4) despite the variation of chi 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-chi La2 chi/3Cu3Ti4O12 ceramics was less than 0.20 in similar to 600-10(5) Hz region, which rapidly decreased to a minimum value of 0.03 by La3+ doping with chi = 0.05. Our measurement of the ceramics conductivities (sigma) also indicated that the appropriate introduction of La3+ into CaCu3Ti4O12 would distinctly result in its dielectric properties. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.