Impedance spectroscopy of n-doped (Ba,Sr)TiO3 ceramics prepared by modified low temperature aqueous synthesis

Low temperature aqueous synthesis (LTAS) has been applied to the preparationof La or Nb-doped (Ba,Sr)TiO3 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. Microstructural characterisation showed the presenceof a secondary phase, identified as a Ti-rich barium titanate compound.Impedance spectroscopy (IS) has been used to study the PTCR behaviourof such materials. IS results are analysed, taking into account effectof the secondary phase, to discuss bulk and grain boundary characteristics.