Negative Temperature Coefficient Thermistors Research Articles

Design of a Negative Temperature Coefficient Temperature Measurement System Based on a Resistance Ratio Model

In this paper, a temperature measurement system with NTC (Negative Temperature Coefficient) thermistors was designed. An MCU (Micro Control Unit) primarily operates by converting the voltage value collected by an ADC (Analog-to-Digital Converter) into the resistance value. The temperature value is then calculated, and a DAC (Digital-to-Analog Converter) outputs a current of 4 to 20 mA that is linearly related to the temperature value. The nonlinear characteristics of NTC thermistors pose a challenging problem. The nonlinear characteristics of NTC thermistors were to a great extent solved by using a resistance ratio model. The high precision of the NTC thermistor is obtained by fitting it with the Hoge equation. The results of actual measurements suggest that each module works properly, and the temperature measurement accuracy of 0.067 °C in the range from −40 °C to 120 °C has been achieved. The uncertainty of the output current is analyzed and calculated with the uncertainty of 0.0014 mA. This type of system has broad potential applications in industry fields such as the petrochemical industry.

Recovery of Ni-Co-Mn Oxides from End-of-Life Lithium-Ion Batteries for the Application of a Negative Temperature Coefficient Sensor

This study demonstrates the current advancements in battery management systems (BMSs), emphasizing the need for precise temperature monitoring within battery packs to enhance safety and performance through efficient thermal management. The increased demand for lithium-ion batteries (LIBs) has driven the development of temperature sensors with improved accuracy and stability. In particular, Ni-Co-Mn-based spinel oxides are commonly used due to their stable negative temperature coefficient (NTC) behavior. However, challenges arise in manufacturing due to the high cost and uncertain supply of critical cathode components (e.g., Co, Ni, and Mn) for LIBs. This research focuses on developing spinel-type (Ni0.6Co0.4Mn2)O4 using recycled Ni-Co-Mn oxides obtained from end-of-life (EOL) LIBs, demonstrating temperature resistance behavior suitable for temperature sensing. The oxides are prepared through hydrometallurgy, oxalate synthesis, and post-heat treatment. Successful integration into spinel-type NTC thermistors suggests broader applications in various industrial fields. A systematic investigation into the synthesis and characterization of recovered Ni-Co-Mn oxides from EOL LIB cathode materials (Li(Ni0.33Co0.33Mn0.33)O2) is presented for NTC thermistor application. Thermogravimetric analysis-derivative thermogravimetry (TGA-DTG) identifies the optimal post-heat treatment temperature. The X-ray diffraction (XRD) patterns confirm a cubic spinel structure of the Ni-Co-Mn oxides, supported by scanning electron microscope (SEM) images showing a uniform microstructure. Also, energy dispersive X-ray spectroscopy (EDS) mapping confirms homogeneous element distribution. Recovered oxide pellets from the sintering process exhibit a single spinel structure, with X-ray photoelectron spectroscopy (XPS) analysis revealing changes in the valence states for Ni and Mn. Resistivity measurements demonstrate semiconductive behavior, which shows a B value (3376.92 K) suitable for NTC thermistor applications. This study contributes valuable insights to black powder recycling from EOL LIBs and its potential in temperature-sensitive electronic devices.

SiO2 and Fe cation synergistically modify the LaMnO3 NTC thermistors with high stability

SiO2 insulator and Fe2O3 dopant was simultaneously used to modify the crystalline phase, morphology and electric properties of LaMnO3 ceramics. Results show that there are several merits after modification. On the one hand, the addition of SiO2 is demonstrated to have multifunction to the LaMn1-xFexO3 (0 ≤ x ≤ 0.5) (LMFO) ceramics. After adding SiO2, the surface of LMFO ceramics tend to be flat, the degree of densification increases, the porosity decreases, and the pores almost disappear. Meanwhile, the resistance drift rate of LaMnO3 with SiO2 is reduced and the aging stability is improved. In addition, the crystalline structure of LMFO ceramics transform from hexagonal perovskite phase (x ≤ 0.2) to cubic perovskite phase (x ≥ 0.25) along with the Fe-doping contents increase. Moreover, the grain size decreases and the grain boundaries increase with the increase of Fe content. X-ray photoelectron spectroscopy (XPS) spectra show that both the Mn4+/Mn3+ ratio and the oxygen vacancy concentration decrease with increasing Fe content. Resistivity ρ25°C raised from 2.84 Ω cm to 65.38 Ω cm, and material constant B25/50 increased from 139.36 K to 1751.78 K. Fe doping significantly improves the stability of LMFO ceramics, and the minimum value of resistance drift rate is 0.168 % after aging at 125 °C for 500 h. The above results confirm that the SiO2 modified LMFO ceramic is a high stability negative temperature coefficient (NTC) thermistor.

Can ZrAlN thin films be used as thermistor sensors for temperature assessment?

The electrical characteristics and conduction mechanisms of ZrAlN thin films for their potential use as thermistor sensors were assessed. Various compositions of Zr1-xAlxN were synthesized by sputtering and studied up to 200 °C to understand their sensitivity and applicability. Among the compositions studied, the ones with x = 0.34 and x = 0.46 showed the highest sensitivities, reaching values close to 3000 K. However, the thermo-resistive properties exhibited by these compositions limited their utilization above 100 °C. Zr1-xAlxN film compositions with x higher than 0.46 showed amorphous structures and were found to be insulative. Composition with x = 0.26, within the cubic phase, showed the most promising electrical properties regarding temperature sensing in the studied range. XPS analysis of this composition confirmed the presence of Zr-N and Al-N bonds, with a Zr3+ oxidation state, which suggests the availability of a free electron contributing to the electrical conduction. Impedance measurements performed at different temperatures for this composition revealed the dominant role of the grain boundaries in the conduction mechanism, based upon electron hopping between grains, overcoming the energy barrier imposed by the grain boundaries. ZrAlN thin films demonstrate negative temperature coefficient (NTC) thermistor behavior, expanding their applications beyond protective coatings to temperature monitoring.

Non-bridge NTC thermistor anemometer with programmable sensitivity

This paper presents a programmable constant temperature anemometer (CTA) with a voltage control of the negative temperature coefficient (NTC) thermistor's working temperature. The CTA uses a non-bridge regulating circuit, outputting voltage, current and power dissipation signals. Its operation and sensitivity control are tested for NTC temperatures in a 45 to 85°C range, at wind speeds up to 14m/s. The power sensitivity at 25m/s is improved by NTC temperature increase, estimated to be 6.74mW/(m∙s−1) at 85°C. A qualitative analysis of circuit's stability is derived, providing the guidelines for bandwidth optimization. The NTC's resistance is regulated with error of 0.9% for working temperatures over 60°C. The demonstrated programmability of NTC temperature allows for implementation of known temperature compensation and measurement techniques utilizing a single sensor, while permitting continuous sensitivity control. This makes it suitable for measurements with varying ambient conditions.

A novel linear temperature thermistor in the xAl2O3-(1-x)CdSnO3 system

Negative Temperature Coefficient (NTC) thermistors, known for their high sensitivity and fast response, find wide applications in national economy, military, aerospace and various other fields. The study of NTC thermistors with linear temperature-resistance is of great significance in streamlining circuit designs and developing high-performance electronic ceramics. This study focuses on the synthesis of a linear thermistor material in xAl2O3-(1-x)CdSnO3 system by a solid-phase reaction method. Through the introduction of th high-resistance Al2O3 phase, a three-dimensional conductive network is established with Al2O3 and CdSnO3, resulting in the acquisition of linear electrical properties. These properties have exhibited excellent linear NTC variation within the temperature range of 308 K–458 K. Notably, at x = 0.2, the thermistor shows the highest linearity (R2 = 0.9984). Additionally, the complex impedance spectral analysis has helped build resistive and capacitive conductivity models revealing the linearization mechanisms.

Synthesis of a scheelite barium molybdate: Structural, topological, electrical, and transport properties for negative temperature coefficient thermistor application

Preliminary structural analysis of Scheelite barium molybdate BaMoO4 (BMO) ceramic using NTREOR-09 and McMaille methods has confirmed the tetragonal symmetry with room temperature X-ray diffraction (XRD) spectrum. Further, other structural parameters like crystallite size and compressive lattice strain are found to be of 31 nm and −0.00151 respectively. The topographical study of scanning electron microscope (SEM) image confirms the polycrystalline nature with no other impurities in the sample. Detailed analysis of dielectric permittivity (εr), and loss (tanδ) supports Maxwell-Wagner and Koop's phenomena. The non-overlapping small polaron tunnelling (NSPT) and correlated barrier hopping (CBH) model have emphasis on transport mechanism. The presence of semiconducting behavior of the scheelite material at various temperatures and frequencies examined by complex impedance and modulus spectra. The value of grain resistance decreases as temperature increases demonstrating the existence of negative temperature coefficient (NTCR) behavior of the material. The increase of the value of thermistor constant (β) (67.339, 516.613, and 772.485 in the different high-temperature range) suggests an efficient application of the material for NTC-thermistor.

Sintering and electrical properties of Mn–Co–Fe–Zn–Ni–O high-entropy ceramics for NTC thermistors

In this work, the dual-phase structure Mn–Co–Fe–Zn–Ni–O high-entropy negative temperature coefficient (NTC) ceramics were synthesized by a solid-phase reaction method. The ceramics are mainly composed of the cubic spinel phase and the rock salt phase. Electron microscopic images revealed the typical morphology and the homogeneous distribution of all elements. The results confirmed that the microstructure and electrical properties of the high-entropy ceramics are closely related to the sintering temperature. As the sintering temperature increased, the content of the rock salt phase gradually improved, meanwhile, the higher resistivity of samples was achieved. Notably, it was found that an appropriate proportion of the rock salt phase could significantly enhance the aging stability of ceramics. The aging drift of the samples sintered at 1175 °C was only 0.632 %. In addition, the ratio of the two phases was adjusted by adding NiO. The ρ25 and B25/50 of the materials can be tuned in the range of 22.25 kΩ cm∼24.19 kΩ cm and 4047 K–4145 K, respectively. Regulating the phase ratio of dual-phase materials is a novel strategy for designing NTC ceramic materials with excellent characteristics. This work provides an idea for future research on high-entropy NTC thermistor ceramics.

High-entropy (Co0.2Mn0.2Fe0.2Zn0.2Al0.2)3O4 thick-film NTC thermistor with high aging stability and wide temperature measurement range

Here, a novel type of high-entropy (Co0.2Mn0.2Fe0.2Zn0.2Al0.2)3O4 solid-solution ceramics with spinel phase structure was designed and successfully fabricated based on an entropy engineering approach. Additionally, the impact of sintering temperature, a critical factor in entropy stabilization, on structural and electrical behavior was systematically examined at a range of 1110∼1150 °C. The results indicate that each synthesized sample exhibits a single spinel structure in the Fd‾3 m (227) space group, and all five metal elements were uniformly distributed, demonstrating entropy stabilization. Meanwhile, the fabricated high-entropy ceramics manifest exceptional negative temperature coefficient (NTC) characteristics in the temperature range of 25 °C–350 °C. The aging stability is excellent as well. After aging at 150 °C for 1000 h, the ΔR/R0 of thick-film samples sintered at 1150 °C is less than 1 %. The successful synthesis of this novel class of spinel-type high-entropy ceramics introduces an emerging design approach for the development of NTC thermistors, particularly for applications in medium-temperature environments.

Online Noninvasive Technique for Condition Monitoring of Cooling System in Urban Rail Vehicles

The open self-ventilated cooling system is an important component to dissipate heat in urban rail vehicles. While after long term operation, the cooling system will deteriorate, which ultimately affects the reliable operation of traction converter. In this paper, we propose a method to monitor the health status of cooling system in urban rail vehicles using the temperature response curve of negative temperature coefficient (NTC) thermistor built in IGBT module. Back Propagation Neural Network (BPNN) is employed to predict the reference curve of healthy state under different working conditions and Discrete Fréchet Distance (DFD) algorithm is applied to achieve the difference comparison. The proposed approach considers the dynamic response process and is suitable for online monitoring. Advantages of the proposed approach include no need to install additional measurement circuit and to heat the module to thermal equilibrium. Moreover, this method enables the concurrent monitoring of multiple components in the cooling system. Simulation analysis and experimental tests are performed to verify the accuracy and effectiveness.

Electrical performance and conductive mechanism of xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 ceramics with NTC effect via chemical modification

xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 (xLCO-(1-x)BCTS) ceramics were manufactured using a solid-phase reaction method. All samples exhibited single cubic perovskite structures and a typical negative temperature coefficient (NTC) effect. The grain sizes increased with increasing LCO doping content. For all samples, the resistivities (ρ25), activation energies for electrical conduction (Ea), thermal constants (B25/75), and activation energies of the relaxation process (Erelax) were in the ranges of 5.93 × 104-9.36 × 108 Ω•cm, 0.3700–0.2951 eV, 3177–3988 K, and 0.3539–0.2890 eV, respectively. Such a combination of ρ and B renders these materials to be potential candidates for NTC thermistors. According to the XPS spectra and due to the difference in ion radius among Co3+, Co4+, Ti3+, and Ti4+, Co3+-O-Co2+ and Ti3+-O-Ti4+ bonds were formed, and the electrons in the continuous bonds generated jumping conduction. The fitted results of the equivalent circuit showed that Rg and Rgb decreased with increasing LCO content, which is consistent with the DC resistivity at 25 °C. The results of the analysis indicate that the conductive mechanism of xLCO-(1-x)BCTS ceramics was electron hopping conduction.

High-stability solid solution perovskite (1-x) Bi0.2Sr0.5La0.3TiO3- xLaMnO3 (0.05≤ × ≤0.2) for wide-temperature NTC thermistors.

The development of negative temperature coefficient (NTC) thermistor materials with a wide range of operating temperatures, high resistance (R), low thermal content (B) and good stability is significant for improving the overall performance of NTC thermistors. Traditional NTC thermistors materials are of the spinel, however, their practical applications are commonly limited to temperatures below approximately 200°C.In this study, it was found that a novel perovskite-structured solid solution (1-x)Bi0.2Sr0.5La0.3TiO3-xLaMnO3 (0.05 ≤ × ≤ 0.2) (BSLT-LM) showed good NTC performance from room temperature to high temperature (600°C) due to the stable structure at high temperatures. The ρ25, ρ100, ρ600 and B25/100, B25/600 constants of Bi0.2Sr0.5La0.3TiO3-0.1LaMnO3 NTC thermistors are approximately 1.76 × 108Ωcm, 1.13 × 107Ωcm, 9.89 × 102Ωcm, 4063.91K, 5472.34K, respectively. The electrical conductivity of these solid solution refers to the electronic transition between Mn3+ and Mn4+, and oxygen vacancies. These results demonstrate the tremendous potential of perovskite-structured (1-x) Bi0.3Sr0.5La0.2TiO3-xLaMnO3 thermistor ceramics with NTC performance.

New high temperature negative temperature coefficient thermistors in Mg0.5Mn0.5AlFeO4 ceramics

For high temperature thermistor applications, the MgAl2O4 exhibits poor conductivity and requires high sintering temperature for ceramic densification. In this study, we have reported on the preparation and characterization of spinel Mg0.5Mn0.5AlFeO4 ceramics by solid solution modification. The resultant ceramics exhibit a combination of high temperature stability and semi-conductivity, which are the characteristics of MgAl2O4 and MnFe2O4. The material has a moderate thermistor constant, which is in favor of application at high temperatures and a wide temperature range. The electrical conductivity is due to the small-polaron hopping in different valence states of manganese and iron ions. Our findings demonstrate a promising approach to extend the applicability of spinel ceramics for high temperature thermistors.

A novel (Sm0.2Eu0.2Gd0.2Ho0.2Yb0.2)CrO3 high-entropy ceramic nanofiber as a negative temperature coefficient thermistor

The electrical properties of high-entropy ceramics (HECs) have been extensively studied in recent years due to their unique structural characteristics and fascinating functional properties induced by entropy engineering. Novel high-entropy (Sm0.2Eu0.2Gd0.2Ho0.2Yb0.2)CrO3 (HE-RECrO3) nanofibers were prepared by electrospinning. This work demonstrates that HE-RECrO3 nanofibers were successfully synthesized at a low temperature (800 °C), which is approximately 400 °C lower than the temperatures at which chromate ceramics were synthesized via the sol–gel method and the solid–state reaction method. The resistivity of HE-RECrO3 nanofibers decreases exponentially with increasing temperature from 25 to 600 °C. The logarithm of the resistivity is linearly related to the inverse of the temperature, confirming the negative temperature coefficient property of HE-RECrO3 nanofibers. The B25/50 value of the HE-RECrO3 nanofibers reaches 4072 K. In conclusion, HE-RECrO3 nanofibers are expected to be potential candidates for negative-temperature-coefficient (NTC) thermistors.

Negative temperature coefficient of ZnO microwires for cryogenic temperature sensing

Negative temperature coefficient (NTC) thermistors are expected to be developed at cryogenic temperature sensing. In this paper, a kind of cryogenic thermistor was developed based on NTC response of single crystal ZnO microwires (MWs). The current–voltage (I–V) characterization demonstrated a NTC response, which was temperature dependence of resistance that decreased with increasing temperature. A sensitive NTC response, especially at the cryogenic temperature range, was observed. The defects in ZnO MWs play an important role in NTC response; therefore, we studied the origin of NTC effect associated with defects to improve the recognition of relationship between defects and the NTC effect and further optimize the temperature sensor design for high performance. Annealing at 800 °C in air was undertaken to make a significant influence on the concentration of defects in as-grown sample, and a series of temperature-dependent features were investigated by photoluminescence, Raman, XPS, and EPR measurements. The results indicated the zinc interstitials to be effective donors for sensitive NTC effect at the cryogenic region. This study provides insight into the ZnO NTC effect and sensitive cryogenic sensing technology.

Form stable phase change material supported by sensible and thermal controllable thermistor

A negative temperature coefficient (NTC) thermistor with thermal sensing and control capabilities was manufactured by adopting form stable phase change materials (PCMs). The incorporation of PCMs expanded their potential uses by providing a stable and continuous circuit. The PCMs underwent a nearly isothermal phase transition process, which lasted for a long time without significant temperature fluctuations. To hold the pure PCM and prevent leakage during melting and cooling processes, a graphene aerogel was employed as a supporting material. Compared with microsphere PCM composite, the graphene aerogel had a high porosity. The PCM composite retained over 98 wt% of the working material for thermal energy. The NTC thermistor probe was inserted into the PCM composite to construct a thermal sensible device. The PCM surrounded NTC thermistor exhibited an excellent thermal stability and could maintain the output current in the circuit. These findings suggest that the form stable PCM composite can be utilized in thermal controllable systems to prevent overcurrent and safeguard electronic devices.

Water-Stable Hybrid Lead-Free Perovskite for Negative Temperature Coefficient Thermistors

Negative temperature coefficient (NTC) thermistors feature higher sensitivities and faster response speeds and thereby have particular applications in many fields. However, current NTC thermistors are mostly based on inorganic ceramic materials, which show obvious drawbacks in material synthesis, property modulation, and flexible film fabrication. Herein, we report, for the first time, the promising application of an inorganic-organic hybrid NTC thermistor. A new lead-free hybrid iodo bismuthate [1,1',1″-(benzene-1,3,5-triyl)tris(3-methyl-1H-imidazol-3-ium)]Bi2I9 [denoted as (Me3TMP)Bi2I9] was synthesized by a "double-free" strategy. (Me3TMP)Bi2I9 features a lead-free binuclear bismuth iodine anion charge compensated by a "classic hydrogen-bond-free" cation. (Me3TMP)Bi2I9 exhibits remarkable stability in water and UV light irradiation and shows the largest temperature sensitivity coefficient among all reported NTC materials. Theoretical calculation and detailed structural analysis disclose that the seriously distorted (BiI6) octahedra are responsible for the intriguing NTC effect for (Me3TMP)Bi2I9.

Electrical properties and thermistor behavior of TiAlN thin films deposited by combinatorial sputtering

A combinatorial deposition was performed by direct current magnetron sputtering (DCMS) to develop Ti1-xAlxN thin films with different Ti/Al ratios and investigate the electrical response to temperature. The crystal structure as a function of the x was studied by X-ray diffraction, and sheet resistance response was measured up to 200 °C. From x = 0.16 to x = 0.56, the film shows an fcc phase with Al in solid solution in the TiN matrix, whilst, from x ≥ 0.69, a mixture of hcp (AlN) and fcc phases is observed. A negative temperature coefficient (NTC) thermistor behavior was found from x = 0.21 onwards, and a maximum sensitivity β of 1600 K was observed for x = 0.56 and 0.69. One fcc sample (x = 0.46) was selected to analyze the chemical states by X-ray photoelectron spectroscopy and the impedance behavior with the temperature by electrical impedance spectroscopy. The crystal structure, bond states and impedance analysis were compared with an AlN thin film. It is concluded that the conduction mechanism for x = 0.46 is based upon electron hopping, and the effect of the grain boundary is more relevant than the grain at low temperatures. We demonstrate that it is possible to use TiAlN as an NTC-thermistor with different crystal structures and chemical compositions.

A Double Perovskite BiFeMoO6: Microstructural, Optical, Dielectric and Transport Properties

In this communication, the synthesis (solid-state sintering) and characterization of a double perovskite BiFeMoO6 are reported. Analysis of X-ray diffraction (XRD) data provides monoclinic crystal symmetry with an average crystallite size of 85.6[Formula: see text]nm and lattice strain of 0.00078, respectively. The microstructural analysis of the sample was done using a scanning electron microscope (SEM) and the results show that grains are well-grown and distributed uniformly throughout the sample surface. The grains are visible clearly due to well-defined grain boundaries, and the effect on the mechanism of electrical ac conductivity was studied. The compositional purity of the sample was checked by energy dispersive X-ray (EDX) analysis spectrum which supports the presence of all constituent elements (Bi, Fe, Mo and O) in both weight and atomic percentages. The study of the Ultraviolet–Visible spectrum provides a bandgap energy of 1.8[Formula: see text]eV, suitable for photovoltaic applications. The measurements of the dielectric were used to confirm the existence of the Maxwell–Wagner type of dispersion. The study of impedance spectroscopy helps to understand the negative temperature coefficient of resistance (NTCR) character while the electrical modulus measurements claimed a non-Debye relaxation mechanism in the sample. The study of ac conductivity reveals the fact of thermally activated conduction mechanism in the sample. The presence of the semiconducting nature of the sample was checked from both Nyquist plots and Cole–Cole plots. The study of the resistance versus temperature reveals the fact of negative temperature coefficient (NTC) thermistor character and is suitable for some temperature sensor devices.

An Adaptive Temperature Observer for Electrothermal Analysis of IGBT Based on Temperature Characteristics

Most of the existing methods for electrothermal analysis of the aging insulated gate bipolar transistor (IGBT) modules have limitations on performing synchronous recognition and decoupling of two typical aging models, and failed to be low-invasive and real-time. To address this, two characteristic functions are developed in this article. The characteristic functions are derived from the temperature response under periodic power loss excitation and can be extracted in real-time and low-invasively from the negative temperature coefficient (NTC) thermistor sensor integrated into the IGBT module. Then, a temperature observer based on the 3-D state-space model of the IGBT module is designed, which is based on the feedback from the characteristic functions, to achieve the target of online electrothermal analysis for the IGBT module even with the significant deterioration of the IGBT module. Finally, the performance of the proposed method is thoroughly investigated by extensive experimental tests.