The jump-like PTCR effect in a Ni-BaTiO3 magnetic composite

Abstract

The ceramic composites BaTiO3@Ni, composed of a conducting nickel and a highly resistive ferroelectric BaTiO3 phase, exhibiting a positive temperature coefficient of electrical resistivity (PTCR), are prepared using a conventional ceramic method at less than 1000 °C. The BaTiO3@Ni composites show a jump-like PTCR effect in electrical resistivity by about eight orders of magnitude (ρmax/ρmin ≈ 108) with ρmin < 1 Ωcm. This is the first example of a standard PTCR element with a relatively high magnetization. The grain relocations (a microstructural rearrangement) on a microscopic scale in the composite are filmed using a transmission electron microscope while heating through the ferroelectric phase transition (Curie temperature), which induces the PTCR anomaly. The resistivity anomaly of the composite is explained in terms of the ferroelectric phase transition-assisted anomaly in the electrical resistivity.

(Ba0.55Sr0.45)1−xLaxTi1.01O3-Bi0.5Na0.5TiO3 Positive Temperature Coefficient Resistivity Ceramics with Low Curie Temperature (~−15 °C)

“…Materials with a positive temperature coefficient of electrical resistance (PTCR) have been widely used as temperature switches or thermistors in overload protectors, selfregulating heaters, starter motors, and resettable fuses [1][2][3]. Their resistances could grow exponentially at T c (Curie temperature) or in a narrow temperature span near the phase transformation temperature.…”