Double critical temperature characteristics of semiconducting (Ba0.7Pb0.3)TiO3 materials prepared by microwave sintering

In this work, we obtain (Ba0.7Pb0.3)TiO3 materials possessing double critical temperature T-c in resistivity-temperature (rho-T) behavior by microwave sintering at 1050-1080 degrees C for 5 min. The cooling-rate control and postannealing processes modify the relative magnitudes of low- and high-T-c resistivity jumps without altering the T-c values. The donor E(d) and trap E(s) levels of those materials are estimated to be Ed congruent to 0.05-0.07 eV and E(s) congruent to 1.07-1.32 eV. According to experimental results the voltage sensitivity and transient responsivity of the current passing through double-T-c materials are observed to be superior to those of single-T-c materials prepared by the conventional furnace sintering method. Also, the double-T-c characteristics are attributed to the dual phases with a core-shell structure, Moreover, the change in the relative proportion of the two phases accounts for the influence of post-heat treatment processes on the materials' rho-T behavior. (C) 1996 American Institute of Physics.