Effects of different bismuth-based compounds additives on the positive temperature coefficient effect of BaTiO_3 ceramics

摘要

As a candidate for lead-free positive temperature coefficient of resistivity (PTCR) ceramics, BaTiO_3 (BT) ceramics with different Bi-based compounds (K_(0.5)Bi_(0.5)TiO_3, BaBiO_3, Bi_4Ti_3O_(12) and Bi_2O_3) were fabricated by a conventional solid state reaction. The effects of Bi-based compounds additives on the phase composition, microstructure and PTCR characteristics of BT ceramics were investigated with X-ray diffraction, scanning electron microscope, and resistivity-temperature measurement instrument. The results showed that the average grain size, the Curie temperature (Tc) and the room temperature resistivity (ρ_(RT)) of BT ceramics varied with the additives of Bi-based compounds. The minimum value of ρ_(RT) for BT ceramics with different Bi-based compounds could be obtained when the atom concentrations of bismuth were around 0.2%. The ceramic samples showed a moderate PTCR effect, with a resistance jump greater by 1.4-3 orders of magnitude and increased Tc about 120-132 ℃, along with a low resistance of 4-1500ncm.