Impedance spectroscopy of n-doped (Ba,Sr)TiO_3 ceramics prepared by modified low temperature aqueous synthesis

摘要

Low temperature equeous synthesis (LTAS) has been appleid to the preparation of La or Nb-doped (Ba, Sr) TiO_3 powders. Doping elements have been mixed to precursors, in order to directly obtain crystalline powders with modified composition. Similar powders, doped by conventional wet ball-milling process, have been also prepared for comparison. Ceramic samples have been obtained by isothermal sintering in air at different temperatures. Micro-structural characterisation showed the presence of a secondary phase, identified as a Ti-rich barium titanate compound. Impedance spectroscopy (IS) has been used to study the PTCR behaviour of such materials. IS results are analysed, taking into account effec tof the secondary phase, to discuss bulk and grain boundary characteristics.