Barium titanate-based thermistors: Past achievements, state of the art, and future perspectives

Abstract

Barium titanate materials displaying a positive temperature coefficient of resistivity are ubiquitously employed as thermistors in electrical current and voltage control systems, as well as in gas and thermal sensing applications. The positive temperature coefficient of resistivity effect is widely accepted to be a grain boundary-based phenomenon, although detailed studies on grain boundary structure and chemistry, and their influence on the resulting electrical properties, are seriously lacking. Tailoring of the positive temperature coefficient of resistivity electrical characteristics, for specific high-value applications, will require improved understanding and control over grain boundary phenomenon. A comprehensive overview of the development of barium titanate-based positive temperature coefficient of resistivity ceramics is initially presented. We then advance to a discussion on emerging grain boundary characterization techniques, specifically, a stereographic analysis of electron backscatter diffraction data that could assist in enhancing control over BaTiO 3 defect chemistry and microstructure, through characterization and subsequent manipulation of the population of grain boundary types. These techniques have great potential for increasing the understanding of the delicate interplay between processing conditions, chemistry, microstructure, and functional electrical properties, and are relevant to the development of advanced, high-performance ceramics and electroceramics in general. Contemporary advancements in the field, such as lead-free positive temperature coefficient of resistivity effect materials and multilayer miniaturized systems based on hypostoichiometric barium compositions, are reviewed. Finally, perspectives on future lines of thermistor research, with a focus on the energy sector, are presented including applications in gas separation and chemical sensing.

Bubble-Printed Microscale Silver Thermistors

“…16 State-of-the-art thermistors are fabricated from barium titanate (BaTiO 3 ), which demonstrates PTC behavior or NTC behavior depending on the nature and concentration of the dopants. 17 However, multiple challenges arise from size effects that inhibit miniaturization of BaTiO 3 thermistors, including compositional inhomogeneity and reduced operational lifetimes. 18 In addition, issues such as contact resistance, inhomogeneous heating, 19−21 and delamination fracture 21,22 arise in practical device applications, rendering BaTiO 3 unsuitable for further thermistor miniaturization.…”

“…PTC thermistors are typically composed of conductive metals or doped ceramics, while NTC thermistors are based on transition metal oxide ceramics that exhibit semiconducting behavior . State-of-the-art thermistors are fabricated from barium titanate (BaTiO 3 ), which demonstrates PTC behavior or NTC behavior depending on the nature and concentration of the dopants . However, multiple challenges arise from size effects that inhibit miniaturization of BaTiO 3 thermistors, including compositional inhomogeneity and reduced operational lifetimes .…”

Changes in the Electrophysical Parameters of Nanomodified Elastomers Caused by Electric Current’s Passage

“…Most electric heaters are based on the PTCR BaTiO 3 effect [ 12 ]. The PTCR effect has built-in protection against overheating: the resistivity of the PTCR material increases by several orders of magnitude near the ferroelectric-paraelectric phase transition temperature (commonly referred to as the Curie temperature TC), which reduces the conductivity and, in turn, the heating current and power by orders of magnitude [ 11 , 12 , 13 , 14 ]. Accordingly, the PTCR heater does not heat up more than TC during normal operation.…”

Detection and Prediction of the Early Thermal Runaway and Control of the Li-Ion Battery by the Embedded Temperature Sensor Array

“…These materials have been extensively researched and designed as potential solutions to effectively mitigate the occurrence of TR in LIBs [1,5]. The PTCR effect is characterized by a significant nonlinear increase in resistance [20] at a certain temperature point or within a very narrow temperature range as the temperature increases.…”

“…For the composite polymers, the PTCR effect stems from the glass transformation of the polymer matrix. This transformation leads to a volume expansion of the polymer matrix, causing the conductive path of conductive particles (acting as filler) to be disrupted [7,20]. It is expected that the resistance of the composite polymer coated on the cathode will rise rapidly to turn off the LIB before the early stage of thermal runaway.…”