PTCR effect in donor doped barium titanate: review of compositions, microstructures, processing and properties

Abstract

Barium titanate is widely used in the fabrication of thermistors with a positive temperature coefficient of resistivity (PTCR). The resistivity can increase by several orders of magnitude near the phase transition temperature (Tc) for the ferroelectric tetragonal to the paraelectric cubic phase transformation. There is general agreement that the anomaly in the change of electrical resistivity of donor-doped BaTiO3 around Tc is due to the grain boundary effect. The Heywang-Jonker model and other mechanisms involving the nature of the electrical barrier formed across the grain boundaries of polycrystalline BaTiO3 are reviewed. The compositional effect on BaTiO3-based PTCR properties is listed and discussed. The influences of manufacturing methods under different stages including the initial doping methods, sample forming methods and final heat treatments on PTCR properties are compared. The complex interrelationship between compositions, microstructures, processing and PTCR characteristics are well discussed.

Enhancement of tetragonal anisotropy and stabilisation of the tetragonal phase by Bi/Mn-double-doping in BaTiO3 ferroelectric ceramics

“…To adjust the electrical characteristics of BaTiO 3 -based ceramic materials, especially to improve their insulating properties, some transition metal elements such as Mn, sometimes accompanied with non-transition metal doping elements, are often added to BaTiO 3 13456. However, adding a small amount of Mn to BaTiO 3 lowers its ferroelectric transition temperature (Curie temperature; T C )7.…”

A Rapid‐Doping Method for High‐Throughput Discovery Applied to Thick‐Film PTCR Materials

“…The sintered density was affected by the doping level and sintering temperature and will be reported elsewhere . Kuwabara found that the magnitude of the PTCR jump reaches a maximum at an optimum sintered density (≈75%–85% of theoretical density) and then decreases with increasing density. This effect has also been reported in another paper in which samples with low porosity have poor PTCR resistivity jump at T c .…”

Anomalous behaviour of dynamic electrical conductivity in semiconductor ferroelectric ceramics near the phase transition temperature

“…Исследование керамики титаната бариястронция (BST) с примесью редкоземельных элементов привлекает пристальное внимание исследователей в течение многих лет [1][2][3][4]. Интерес вызван тем, что выше температуры Кюри наблюдается резкое увеличение сопротивления образцов т. е. имеет место эффект положительного температурного коэффициента сопротивления (ПТКС), что обеспечивает возможность широкого прикладного использования.…”