PTC Thermistor Research Articles

Development of a complex strontium bismuth molybdate material: Microstructural, electrical, and leakage current characteristics for storage and electronic device application

In this article, synthesis (solid-state reaction) and characterizations of a complex strontium bismuth molybdate material have been reported. The scanning electron microscopic image suggests the existence of grains of various sizes and shapes that are evenly dispersed, accompanied by small pores. The Maxwell-Wagner dielectric dispersion, relaxation, and transport mechanism have been investigated utilizing dielectric, impedance, and conductivity spectrum within the studied experimental frequency (1 kHz–1 MHz) and temperature (25–500 °C) range. The energy storage efficiency is 56.13 %, calculated by the loop of electric polarization. The results of temperature-dependent resistance suggest that the prepared material can be used for PTC thermistors, sensors, and other related devices. The varistor constants β1 and β2 indicate the presence of non-Ohmic and SCLC conduction mechanisms, which are also suitable for electronic devices.

The Specifics of PTC Thermistor Applications for Limiting Surge Currents

This paper investigates the possibilities of limiting emergency short current pulses by using materials with a positive temperature coefficient. A computational model and method for simulating this process were proposed. Barium titanate was considered a promising material for current-limiting devices due to its low cost, ease of manufacturing and autonomy. The current-limiting properties of a PTC thermistor device were estimated in relation to a significant pulse current overload (10 ms). The value of taking into account the varistor effect when modeling energy dissipation by a PTC thermistor is experimentally demonstrated. The results of the experiment were used in the development of computer models of the current-limiting properties of PTC thermistors. A method for taking into account the varistor effect in the developed models is proposed. It is noted that in order to increase the accuracy of the calculation, it is important to take into account the heat transfer between the PTC thermistor and its contact system. It is also shown that this heat transfer is capable of creating a significant longitudinal temperature gradient inside the PTC thermistor, which creates a high level of thermal stress and leads to mechanical failure. Destruction of this type has been observed during experiments. This research was carried out within the state assignment FSEG-2023-0012.

Investigation of structural, topological, and electrical properties of scheelite strontium molybdate for electronic devices

This article describes the synthesis (solid-state reaction) and characterizations of a scheelite strontium molybdate. The consistency of lattice parameters by N-TREOR09 and the Le-Bail Rietveld refinement method supports the tetragonal crystal system. The spectrum of the pair distribution function (PDF) depicts the orientations of atoms within a tetragonal symmetry. The Williamson-Hall plot examines the average crystallite size (86 nm) and micro-lattice strain (0.00091). The scanning electron microscopic image, energy dispersive X-ray (EDX) spectra, and elemental mapping confirm the uniform and isotropic characteristics of the synthesized material, purity and compactness, and topographic roughness according to ISO25178 standards. The investigation of dielectric, impedance, and conductivity spectra confirms the presence of Maxwell-Wagner dielectric dispersion, relaxation, and influential transport phenomena across a broad spectrum of experimental frequencies (ranging from 1 kHz to 1 MHz) and temperatures (from 25 °C to 500 °C). The observed temperature-dependent resistance characteristics validate that the prepared material is well-suited for applications involving PTC thermistors, sensors, and other related devices. The scaling properties of the modulus data provide evidence for a non-Debye relaxation mechanism. The values of the varistor constant, β1, β2, and β3, which are 1.414, 2.362, and 9.654, respectively, indicate the existence of Ohmic conduction, trap-limited space charge limited conduction (SCLC), and trap-filled SCLC mechanisms suitable for electronic devices.

Effect of gradient distribution of fillers on polymeric PTC thermistors prepared by solution mixing and subsiding method

The PTC materials are widely utilized in regulating components of heat and electricity by virtue of the special resistivity-temperature characteristics. The high room temperature resistivity and low PTC intensity restrict the application of polymeric PTC thermistors. A solution mixing and subsiding method was developed to fabricate the thermistors with different gradient distributions of TiC and CB fillers in PVDF matrix, owing to the low viscosity of dispersion and the difference in density of fillers and solution. The easily settleable TiC assembled at the interface of copper foil and PTC material could provide abundant conductive sites to significantly reduce the interface resistances. The difficultly settleable CB uniformly distributed over the matrix could effectively decrease the bulk resistance. Through adjusting the subsidence time and filler compositions, the optimal conductivity (ρ = 0.58 Ω cm) and PTC intensity (7.0) of polymeric PTC thermistor were obtained. Moreover, the switch temperature was markedly improved and the NTC effect was weakened.

PTC서미스터 히터소자를 적용시킨 전기온풍기의 발화 매커니즘 연구

Electric heaters with PTC thermistor heater elements have been widely used for heating at home and businesses, replacing heating devices using fossil fuels. The PTC thermistor heater device maintains a constant temperature by controlling a heating value by increasing or decreasing the current as the resistance value changes to limit the amount of current. In this paper, since a fire occurs due to indiscreet use of the device, careless use of the PTC thermistor heater device-type electric heater and the defect state of the device itself were presented. After that, the heating characteristics and the possibility of firing were analyzed through lots of experiments. As the separation distance from the combustible material approached, the temperature of the combustibles material increased proportionally. However, the temperature of the PTC thermistor heater element itself was kept constant. In addition, even if serious overheating conditions were set, the temperature overheating prevention device of the device itself was operated, which did not lead to abnormal overheating and firing of the heater device itself. It could be verified through empirical experiments that the firing could be caused by arc generation between PTC heater device and adjacent electrode, as an abnormal current occurs under conditions where the resistance of thermistor itself is interfered with by the inflow of external conductive materials. In conclusion, based on the results of the reproduction test, matters to be considered when improving the fire investigation and fire prevention system were presented.

Sensing Characteristics of Improved Positive Temperature Coefficient Thermistors with Paint Forms.

The disadvantage of using a typical temperature sensor is limited depending on the shape of the model to be measured. If the shape is curved, it is not easy to check the surface temperature. A smart paint for temperature measurement is proposed to overcome this disadvantage. Polymer solutions were prepared with a dispersion of materials and viscosity with the properties of paint forms. The smart paints showed various sensing characteristics depending on the amount of materials. In addition, it was analyzed through the scanning electron microscopy (SEM) that sliver particles are disposed around the ceramic particles to have electrical conductivity. This study optimized the proportion of ceramics added to smart paints so that they could overcome the limitations of PTC thermistors that can only identify specific temperatures. Therefore, the developed paint-type temperature sensor makes it easy to measure the temperature of various models.

First-principles calculations of ferroelectricity and structural stability in Bi- and Alkali-Metal-Modified BaTiO3 for PTC thermistor applications

First-principles density functional theory (DFT) was used to seek the possibility of enhancing ferroelectricity, structural stability, and TC of BaTiO3 by Bi/alkali-metals co-doping. From the results, among M = Li, Na, K, Rb, and Cs, we found that K gives the largest c/a ratio (tetragonality) and spontaneous polarization (Ps), which these c/a and Ps are also larger than those from pure BaTiO3. In addition, the calculated solution energy (at Ba-poor condition) reveals that the incorporation of Bi and K on A site yields the most stable structure. The predicted enhancements of ferroelectricity and structural stability in the case of Bi/K modified BaTiO3 is found to be weakly dependent on how Bi and K are arranged to occupy different positions of A site in the supercell. Consequently, our results suggest that K is the best candidate. The findings can then be used to suggest ways of enhancing ferroelectricity, structural stability, and TC in BaTiO3 ceramics for broadening the operating temperature of BT-based PTC thermistor.

Ferroelectric phase-transition-assisted anomaly in the electric resistivity (FPTAA) of lead-free PTC thermistors

Ceramic composites in the BaTiO3–(Bi1/2Na1/2)TiO3 system exhibiting a positive temperature coefficient of electrical resistivity effect were prepared using a conventional solid-state reaction method. The composite samples were sintered in nitrogen to achieve their final-phase properties, a high resistivity jump of ∼ 103 at about 170 °C. The resistivity anomaly of the composite composed of a conducting network based on a conducting BaTiO3 and a highly resistive ferroelectric phase with a Curie temperature (TC) of 170 °C was explained in the light of ferroelectric phase-transition-assisted anomaly in the resistivity (FPTAA).

Nanocrystalline semiconducting donor-doped BaTiO3 ceramics for laminated PTC thermistor

This paper proposed a two-stage thermal processing method combined with the reduction-reoxidation procedure. Samples were firstly sintered in a reducing atmosphere by two stages and then reoxidized in air. Such two-stage thermal processing method was used to adjust density and grain size of ceramics separately. Finally, nanocrystalline semiconducting donor-doped BaTiO3 ceramics were first successfully prepared. Samples with average grain size of 340nm exhibited unexpectedly low room resistivity of 136Ωcm and a significant PTCR effect, with a resistance jump of 4 orders of magnitude. In addition, depletion layer thickness of 40nm and surface acceptor-state densities of 9.52×1013cm−2 were also calculated. Such good properties had not been reported in former publications. It also means that smaller components based on semiconducting BaTiO3 ceramics could be produced and more extensive application field could be proposed in the trend of miniaturization of electronic devices.

Features of the electrical resistance in magnetoelectric ceramics (1-x)BiFeO3-xMgFe2O4

ABSTRACTResistivity study of two-phase ceramics (1-x) BiFeO3 - x MgFe2O4 showed the presence of PTC thermistor anomaly at a temperature of 260°C, which is less than the phase transition temperatures in the starting components of the system. To elucidate the nature of the thermistor anomaly, the measurements of samples annealed in reducing H2 or CO2 atmosphere carried out. The physical picture of the observed resistivity maximum is discussed.

A compact wideband precision impedance measurement system based on digital auto-balancing bridge

The ac impedance spectroscopy measurements are predominantly taken by using impedance analyzers based on analog auto-balancing bridge. However, those bench-top analyzers are generally complicated, bulky and expensive, thus limiting their usage in industrial field applications. This paper presents the development of a compact wideband precision measurement system based on digital auto-balancing bridge. The methods of digital auto-balancing bridge and digital lock-in amplifier are analyzed theoretically. The overall design and several key sections including null detector, direct digital synthesizer-based sampling clock, and digital control unit are introduced in detail. The results show that the system achieves a basic measurement accuracy of 0.05% with a frequency range of 20 Hz–2 MHz. The advantages of versatile measurement capacity, fast measurement speed, small size and low cost make it quite suitable for industrial field applications. It is demonstrated that this system is practical and effective by applying in determining the impedance-temperature characteristic of a motor starter PTC thermistor.

Chip-Level Active Temperature Control for Improving Temperature Robust of a Micro-Gyroscope

Silicon micro-fabricated gyroscope are very sensitive to ambient temperature, this paper conducted a novel active temperature controlling system. Combined with the PTC thermistor to detect internal temperature and the inserted TEC to control the temperature, encapsulation condition inside the gyroscope was kept in a stable situation. Experimental results showed that it greatly improved the performance of the micro-gyroscope.

PTCR ceramics produced from ultrasound activated barium titanate powders

We have produced PTC thermistors from conventional and ultrasound activated barium titanate powders and have shown that the use of activated starting materials is an effective approach for improving the performance of PTC thermistors.

Experimental Study on HVAC System for Electric Vehicles

An HVAC (heating ventilation and air conditioning) system for electric vehicles based on heat pump technology is designed and set up in this paper. Unlike the existing HVAC system for vehicles using fossil fuel, this experimental HVAC system can work in heat pump mode rather than directly heating the PTC thermistor by electricity when heating is needed. This experimental HVAC system takes use of parallel flow exchangers, enclosed DC vortex compressor and the low voltage DC speed controller, which is used for controlling the compressor`s working frequency. After the experimental system is set, the influence of compressor`s speed and the environmental temperature to the performance of the HVAC system are tested and researched in refrigeration mode and heat pump mode respectively. Parameters like the compressor`s power input, the system`s refrigeration/heating capacity, and the coefficient of performance (COP) varied with compressor`s speed are recorded. Curves of those parameters are drawn and the reasons of their changing trends are analyzed respectively. The testing results of this experimental HVAC system are compared with references` results. According to the testing results, this experimental HVAC system can achieve better refrigeration and heating effects, and the cooling performance of the system increases with compressor speed; Part of the outside heat-exchanger gets frosted when the system works in heat pump mode, but the COP remains greater than 1, which means this experimental HVAC system is more energy-saving than the existing HVAC systems which are directly heating PTC thermistor by electricity for heating; In addition, compared with the sliding-vane compressor, the vortex compressor used in this paper has a better comprehensive performance and hence has a better application prospect.

Production of BaTiO<sub>2</sub> Nanocrystalline Powders by High Energy Milling and Piezoelectric Properties of Corresponding Ceramics

Barium titanate (BaTiO3 or BT) has become one of the most studied functional materials due to its potential application as multilayer ceramic capacitors, PTC thermistors, electromechanical devices, piezoelectric transducers, actuators, dynamic RAM or logic circuitry as well as a great variety of electro-optical devices. In the present study, high energy ball milling has been used to produce nanocrystalline powders of BT. Two categories of powders having average particle size of 35 nm and 25 nm were prepared by setting the milling speed at 250 rpm and 300 rpm respectively, fixing the milling time at 30 hours. Four ceramic samples, BT35-1350, BT25-1350, BT35-1400 and BT25-1400, were formed by sintering the two types of powders at 1350oC and 1400oC for 3 hours. The ferroelectric and piezoelectric properties of the ceramic samples were studied and found to be dependent on the size of the starting nanopowders. The bulk density and piezoelectric constant (d33) of B25-1350 were found to be less than those of BT35-1350, while the reverse was true in case of BT25-1400 and BT35-1400. Well saturated P-E hysteresis loops were observed for all the ceramics with the size and shape of the loops appearing different for the four samples. For both the pairs of ceramics sintered at 1350oC and 1400oC, the remnant polarization (Pr) decreases with starting particle size, that is, as we go from BT35-1350 to BT25-1350 as well as from BT35-1400 to BT25-1400. However, with decreasing particle size of the starting powders, the coercive field (Ec) increases for the ceramics sintered at 1350oC and decreases for the ceramics sintered at 1400oC. The study reveals the importance of an optimized combination of the size of the starting nanopowders and sintering temperature for obtaining BT ceramics with the desired properties.

적층 PTC 써미스터의 전기적 특성에 대한 재산화의 영향

The alumina substrates that Ni electrode was printed on and the multi-layered PTCR thermistors of which composition is were fabricated by a thick film process, and the effect of re-oxidation temperature on their resistivities and resistance jumps were investigated, respectively. Ni electroded alumina substrate and the multi-layered PTC thermistor were sintered at for 2 h under $PO_2

BaTiO3PTC 써미스터의 미세구조 및 전기적 특성에 대한 SiO2영향

PTCR ceramics of <TEX>$(Ba_{0.998}Sm_{0.002})TiO_3+0.001MnCO_3+xSiO_2$</TEX> (x=1, 2, 3, 4, 5, 6 mol%) were fabricated by solid state method. Disk samples of diameter 5 mm and thickness about 1mm were sintered at <TEX>$1,290^{\circ}C$</TEX> for 2 h in reduced atmosphere of <TEX>$5%H_2-95%N_2$</TEX> followed by re-oxidation at <TEX>$600^{\circ}C$</TEX> for 30 min. in <TEX>$20%O_2-80%N_2$</TEX>.and their microstructures and electrical properties were investigated with SEM and Multimeter. The color of sintered samples was strongly dependent on <TEX>$SiO_2$</TEX> content showing that the color of samples with <TEX>$SiO_2$</TEX> of 1~2 mol% was gray but that of samples with <TEX>$SiO_2$</TEX> of 4~6 mol% was changed from gray to blue, which seems to be related with the reduction of samples due to the oxygen vacancies created during the sintering in reduced atmosphere. <TEX>$SiO_2$</TEX> content had a great influence on the microstructure and the electrical properties. With increasing <TEX>$SiO_2$</TEX> content, the grain size of samples increased and the resistivity as well as the resistivity jump (<TEX>$R_{285}/R_{min}$</TEX>) decreased, which is considered to be attributed to the resistivity change at grain interior and grain boundary due to the fast mass transfer through <TEX>$SiO_2$</TEX> liquide phase during the sintering. Samples with 2 mol% <TEX>$SiO_2$</TEX> has the resistivity of <TEX>$202{\Omega}cm$</TEX> and the resistivity jump of 3.28. It is expected that <TEX>$SiO_2$</TEX> doped <TEX>$BaTiO_3$</TEX> based PTC ceramics can be used for multilayered PTC thermistor due to the resistance to the sintering in reduced atmosphere.

적층 SMD형 PTC 써미스터의 열처리 조건에 따른 PTCR 특성 변화

Electrical properties of the laminated SMD-type PTC thermistor for microcircuit protection were investigated as a function of calcination and sintering temperature. BaTiO₃ with Y₂O₃ and MnO₂ were calcined at 1000 to 1150℃ for 2h and the laminated SMDtype PTC thermistor was sintered at 1350 to 1400℃ for 2h in a reduced atmosphere (1% H₂/N₂). Sintered density of the sample was dependent on the calcination and sintering temperature. Electrical properties of the sintered samples were strongly dependent on thedensities of samples. For the samples with density below 4.6 g/㎤, the insulator characteristics were observed, while PTC jump characteristics (R150/R30) were disappeared for the sample with density above 5.05 g/㎤, Optimal PTC characteristics were obtained for the sintered samples with density of 5.05 g/㎥. The laminated SMD-type PTC thermistor prepared by calcination at 1100℃ for 2h and sintering at 1270℃ for 2h showed the room temperature resistivity of 11 Ωㆍcm and PTC jump characteristics of 10 2 order.

History and Future Prospect of Electro-ceramics in Japan and Asia

On the background of a long history of Japanese ceramics, various electro-ceramic materials have been studied and many kinds of electronic components using them have been developed in Japan. The first invention of electro-ceramics in Japan should be a ferrite at Tokyo Institute of Technology in 1930, and the mass production of ferrite started in 1937. Then, Japanese electro-ceramic industry has led the world on electro-ceramic materials and components until now, especially in the fields of BaTiO3, PZT, PTC thermistor, ZnO varistor and insulating ceramics. In recent years, new electro-ceramic materials, their processes and new devices using them have been still studied actively in Japan. Currently, R&amp;D activities in Asia outside of Japan, and electro-ceramic industries in those areas have been grown steadily.

Effect of Hydrolysis on High-Purity TiO&lt;sub&gt;2&lt;/sub&gt; Size for PTC Thermistor

The effect of self-generated seeded thermal hydrolysis factors, such as TiOSO4 solution concentration, grey aging time, volume ratio of TiOSO4 to pre-adding water, and heating rate on high-purity TiO2 size for PTC thermistor were studied. The samples were characterized by particle size distribution, and SEM. The results show that with increase of TiOSO4 solution concentration, the high-purity TiO2 size decrease gradually, but with increase of grey aging time and volume ratio of TiOSO4 to pre-adding water respectively, the high-purity TiO2 size also increase. The suitable TiOSO4 concentration is 160g/l, grey aging time is 15min, the optimum volume ratio of TiOSO4 to pre-adding water is 4.0:1 and heating rate should be 1.5°C/min.