Abstract
This work successfully obtains a positive temperature coefficient of resistivity characteristics with critical temperature (T c .) at around 490 and 420°C for PbTiO 3 (PT), and (Pb 0.9 Sr 0.1 )TiO 3 (PST) materials, respectively. The tetragonality of these materials are (c/a) PT =1.065 and (c/a) PST =1.046. In addition, the donor level of Y 3+ ions in PT materials [(E d ) PT =0.09-0.11 eV] is smaller than that in PST materials [i.e., (E d ) PST =0.29-0.40eV]. The resistivity jumping ratios of the two materials are similar, that is, (ρ max /ρ min ) PT ≅10 2.2 and (ρ max /ρ min ) PST ≅10 1.6 . Multiple-T c resistivity-temperature (ρ-T) characteristics are observed, that is ascribed to the formation of an incomplete core-shell microstructure with the Pb-deficient shell not entirely surrounding the stoichiometric core. © 1998 American Institute of Physics.