Qi Jianquan

Enhancement of positive temperature coefficient resistance effect of BaTiO3-based semiconducting ceramics caused by B2O3 vapor dopants

Abstract The positive temperature coefficient resistivity (PTCR) effect of semiconducting BaTiO3 ceramics can be remarkably influenced by both dopants and ceramic processing. The behavior of B2O3 as vapor dopants was studied in this paper. It was found that the PTCR effect was enhanced distinctly, while the room temperature resistance also increased.

Acceptor compensation in (Sb,Y)-doped semiconducting Ba1−xSrxTiO3

The characteristics of semiconducting Ba1-xSrxTiO3 samples with different doping procedures were studied. Complex impedance-measurements were used to separate the resistances of grains Rb, and grain boundaries as Rgb. It was shown that excess donors added after calcination diffused into the grain bulk more slowly and could be compensted on the grain boundary by acceptors, and thus samples with particularly low resistivity were obtained. Using an excess donor to compensate for the acceptor, a sample with room temperature resistivity of ∼200 Ω cm-1 and greater than 7.8 orders of jumping of resistance was obtained.

Influence of manganese on PTCR effect in BaTiO3-based ceramics doped with Bi2O3 vapor

Abstract The positive temperature coefficient resistance (PTCR) effect of BaTiO 3 -based ceramics is strongly influenced by the doping of donor and acceptor. Some 3d acceptors such as Mn, Fe, Cu can enhance it greatly, whereas this is not the case for the other acceptors such as K, Na, Ni, Mg. The effect can also be enhanced by the doping of Bi 2 O 3 vapor during sintering in BaTiO 3 -based ceramics; in this case, the enhancement of PTCR effect of the sample codoped with manganese is much greater than that only doped with donor. This is because that excess donor can be compensated by codoped manganese and form more stable composite trap centers, and the PTCR effects can be enhanced more distinctly.

The oxidizing of grain boundary defects in BaTiO3-based PTCR ceramics

Abstract The oxygen pressure during sintering influences greatly on the positive temperature coefficient resistance (PTCR) effect of BaTiO3-based ceramics. Using Bi2O3 vapor acting as excess donor resulted in the dense samples with the resistance jumping > 8 magnitude orders and the room temperature resistivity ∼ 100•Cm. The oxidized-defects at grain boundary acting as trap centers, would be responsible for the PTCR effect in BaTiO3 ceramics.