Negative Temperature Coefficient Thermistors Research Articles

EMC Protection of SCB Explosive Devices by Using SMD-Based NTC Thermistors

This paper proposes a surface mount device-based negative temperature coefficient thermistor as an electromagnetic compatibility protection element for semiconductor bridge (SCB) explosive devices. Because of the small size, it can be integrated into the ceramic housing of the SCB without increasing packaging size and affecting normal firing conditions of SCB. This paper demonstrates the usefulness of the protective method by firing experiments, temperature measurements, and RF sensitivity tests.

Acceleration of applied voltage on metallic ion migration of wires in NTC thermistor temperature sensors

The research on NTC (Negative Temperature Coefficient) thermistors often used in temperature sensors has usually focused on performance, and almost no research have been previously done with the focus on reliability, even though field failures of NTC thermistors caused by ion migration are increasing. Therefore, this paper focuses on ion migration between wires, which has a close relationship with field failures of NTC thermistors by measuring the time when ion migration occurs according to different distances between wires and the applied voltage, and quantitatively analyzing the mechanism of ion migration occurrence, acceleration and correlation with ion migration due to applied voltage. Ion migrations between Cu wires occur because of the absorption and condensation of water. Also, due to the inherently brittle characteristics of the dendrite, repeated separation and coalescence were observed. The results of estimating the time of ion migration according to the applied voltage using both Weibull distribution and the same shape parameter showed a good match with the inverse power model, and an index and a specific parameter expressing the sensitivity of ion migration occurrence could be extracted by analysis.

Electrical properties of Sr x Ba1 − x Fe 0·6 Sn 0·4 O3 − ε NTC thermistors

Polycrystalline thermistor ceramics with the stoichiometric formula, Sr x Ba1 − x Fe0·6Sn0·4O3 − ε (0·2 ≤ x ≤ 0·8), had been prepared by a standard solid state reaction route. X-ray diffraction analysis indicates that the ceramic system remains cubic perovskite structure with a very small lattice change. The electrical properties of Sr x Ba1 − x Fe0·6Sn0·4O3 − ε thermistors were studied using a digital thermometer over a wide range of 298–400 K. The thermistors showed an excellent negative temperature coefficient (NTC) thermistor behaviour. The values of resistivity at 298 K (ρ 298), thermistor constant (B 298/358) and activation energy (E a) of the Sr x Ba1 − x Fe0·6Sn0·4O3 − ε thermistors, decreasing with the increase of Sr content, were in the range of 0·37–11·0 kΩ ·cm, 2466–3703 K and 0·212–0·319 eV, respectively. For the thermistors with the compositions x = 0·2 and 0·4, the fitting equivalent circuit was composed of three RCPE elements corresponding to grain, grain boundary and ceramic–electrode interface, respectively. From the impedance plots, it was found that the fitting data showed good agreement with the experimental data. The extracted grain boundary resistance exhibited a NTC thermistor behaviour.

LaNiO3 conducting particle dispersed NiMn2O4 nanocomposite NTC thermistor thick films by aerosol deposition

Nickel manganite spinel (NiMn2O4) based negative temperature coefficient (NTC) thermistors have good thermistor characteristics and stabilities. However, to achieve thermistors with a high B constant, the activation energy should be high, which results in high room temperature (RT) resistivity. To obtain a high B constant and low RT resistivity, NiMn2O4 based nanocomposite thick films with the conducting metal oxide, LaNiO3, were fabricated on a glass substrate by aerosol deposition at room temperature. The NiMn2O4–LaNiO3 nanocomposite thick films showed an RT resistivity as low as 35kΩ cm, which is one order of magnitude lower than that of the NiMn2O4 films, while retaining the high B constant of NiMn2O4 of over 5000K when 25vol.% LaNiO3 was used without any post thermal treatment.

Studies on the properties of Ni0.6Cu0.4Mn2O4 NTC ceramic due to Fe doping

The influence of the Fe on the microstructure, electrical and dielectric properties of Ni0.6Cu0.4FeyMn2−yO4 (0.1≤y≤0.5) negative temperature coefficient (NTC) thermistors prepared by well known simple chemical co-precipitation method were studied. The replacement of manganese by iron plays an important role in changing the lattice parameter, X-ray density, sintered density, porosity, DC resistivity at different temperatures and dielectric properties at different frequencies. The X-ray and sintered density increased linearly and porosity decreased with iron. The room temperature resistivity of nickel copper manganite NTC ceramic decreased from 1MΩcm to 68KΩcm and dielectric constant increased from ∼9×107 to 1.5×109 at 20Hz as iron content increased.

Electrical Properties of Mn3−xCoxO4 (0 ≤ x ≤ 3) Ceramics: An Interesting System for Negative Temperature Coefficient Thermistors

Single‐phase spinel manganese cobalt oxides Mn3−xCoxO4 dense ceramics were prepared for the first time and their structural/electrical property relationships characterized. The electrical properties, that is, the resistivity at 25°C, the energetic constant, and the resistance drift at 125°C, were determined and correlated with the cation distribution. Finally, the electrical characteristics of the Mn3−xCoxO4 system were compare'd with other important classes of manganese‐based spinel oxides, Mn3−xNixO4 and Mn3−xCuxO4, already commercialized as negative temperature coefficient (NTC) thermistors. The high values of energetic constant and low resistivities observed in Mn3−xCoxO4 ceramics present a promising interest for such industrial applications.

The investigation of Zn content on the structure and electrical properties of Zn x Cu0.2Ni0.66Mn2.14−x O4 negative temperature coefficient ceramics

The effects of Zn content on the structure and electrical properties of Cu–Ni–Mn–O based negative temperature coefficient thermistors were investigated. Series of Zn x Cu0.2Ni0.66Mn2.14−x O4 (0 ≤ x ≤ 1) ceramics were prepared by Pechini method. Cu2p3/2 X-ray photoelectron spectra demonstrate that Cu+ and Cu2+ ions at A sites decrease with increase of x, and all the Cu ions exist as Cu2+ (B) at x of 1.0 due to the almost exclusive occupation of Zn ions at A sites. X-Ray diffraction spectra show that a single cubic spinel structure is formed at a low Zn content (x ≤ 0.6), and NiO and CuO start to appear at x of 0.8. The segregation of NiO at x ≥ 0.8 is caused by the migration of Cu ions for A to B sites. With Zn content x increasing from 0 to 1.0, the electrical resistivity increases from 42 to 980 Ω cm which can be attributed to the decrease of the electrical conduction caused by Cu ions at A sites. The resistivity drift decreases sharply from 12.6 to 4.2% with increasing x from 0 to 0.4, and the value is only 0.16% at x of 1.0.

Effects of Mg substitution on microstructure and electrical properties of NiMn2−xMgxO4 NTC ceramics

Abstract

A gain control and stabilization technique for Silicon Photomultipliers in low-light-level applications around room temperature

An experimental setup in dark condition was established to investigate the temperature and bias voltage dependence of the Multi-Pixel Photon Counter (MPPC), one type of the SiPM developed by Hamamatsu. The dark current of an MPPC near room temperature at a given gain can be approximated by an exponential function of temperature which is similar to the behavior of a negative temperature coefficient (NTC) thermistor. According to these facts, a gain control and stabilization circuit for MPPC is developed by using a programmable current sink with temperature compensation. Detailed design and performance analysis results of the circuit in the temperature range from 5.1°C to 33.3°C will be discussed in this paper.

Microstructure and Electrical Properties of Mn<SUB>2.25-x</SUB>Ni<SUB>0.75</SUB>CoxO<SUB>4</SUB> Thermistor Ceramics

A series of composite of the negative temperature coefficient (NTC) powders of Mn2.25-xNi0.75CoxO4 (0.8&lex&le1.2) materials were prepared via solid-state method. The particle size of calcined powders, ceramics phase structure, morphology and electrical properties were characterized by laser particle size analyzer, XRD, SEM and electrical measurements, respectively. The results show that when the Mn2.25-xNi0.75CoxO4 ceramics sintered at 1130-1230°C, their characteristic parameters B25/50 value are found to be in the range of 3487 K to 4455 K and their electrical resistivities ρ25°C are 1998 Ω·cm to 203617 Ω·cm. The B25/50 value and ρ25°C first increases and then decreases as the Co content increases. This means that electrical resistivity and B value of Mn2.25-xNi0.75CoxO4 ceramics could be adjusted to the desired values and this ternary system can be considered as the advanced semi-conducting materials for NTC thermistor applications.

Design and Development of Thermistor based Power Meter at 140 GHz Frequency Band

Design and development of thermistor based power meter at 140 gigahertz (GHz) frequency band have been presented. Power meter comprises power sensor, amplifier circuit and dialog based graphical user interface in visual C++ for the average power measurement. The output power level of a component or system is very critical design factor. Thus there was a need of a power meter for the development of millimeter wave components at 140 GHz frequency band. Power sensor has been designed and developed using NTC (Negative Temperature Coefficient) thermistors. The design aims at developing a direct, simple and inexpensive power meter that can be used to measure absolute power at 140 GHz frequency band. Due to absorption of 140 GHz frequencies, resistance of thermistor changes to a new value. This change in resistance of thermistor can be converted to a dc voltage change and amplified voltage change can be fed to computer through data acquisition card. Dialog based graphical user interface (GUI) has been developed in visual C++ language for average power measurement in dBm. WR6 standard rectangular waveguide is the input port for the sensor of power meter. Temperature compensation has been achieved. Moderate sensor return loss greater than 20 dB has been found over the frequency range 110 to 170 GHz. The response time of the power sensor is 10 second. Average power accuracy is better than ±0.25 dB within the power range from −10 to 10 dBm at 140 GHz frequency band.

Electrical Properties of La(Cr,Mn)O<sub>3</sub> NTC Materials

We investigated the electrical properties of the perovskite R(Cr,Mn)O3(where R is selected from various rare earth elements and Y), which is suitable for use in negative temperature coefficient (NTC) thermistors. The substitutions of Mn for Cr in La(Cr,Mn)O3and larger ions for R3+decreased both the resistivities (r) and thermistor constants (B values) estimated from measurements at 25°C and 50°C according to r = r0exp(B/T). The activation energies of the carrier number (Eg) and carrier mobility (WH) were estimated by measuring the thermoelectric power and resistivity. A change in WHcorresponded to a change in the B value. We discussed the relationship between the grand state electronic configuration of the M3+ions and the local lattice distortion around the M3+ions. The change in WHcould be qualitatively linked to the M3d– O2p transfer energy, which is corresponding to the hybridization between the M3d and O2p orbital (M: transition metal elements, O: oxygen).

In-plane impedance spectroscopy in aerosol deposited NiMn2O4 negative temperature coefficient thermistor films

Temperature dependent in-plane impedance spectroscopy measurements were carried out in order to analyze the charge transport properties of functional oxide NiMn2O4 negative temperature coefficient thermistor films deposited via aerosol deposition techniques onto glass and Al2O3 substrates. The in-plane resistivity (ρ) versus temperature (T) curves of all films were uniform over a large temperature range (180 K to 500 K) and showed the typical exponential power-law behavior associated with variable-range hopping. The ρ-T dependences of annealed and as-deposited films exhibited power-law exponents p of about 0.6 and thermistor constants B in the range of 3500 K to 5000 K. As-deposited films showed higher p values as compared to annealed films. As-deposited films exhibited also increased B values, leading to increased sensitivity of the resistance to temperature changes, whereas annealed films deposited on Al2O3 showed the lowest scatter in differentiated ρ-T data and might display superior reliability for temperature sensing applications.

Fabrication and Characterization of NiMn_2O_4 NTC Thermistor Thick Films by Aerosol Deposition

Negative temperature coefficient (NTC) materials have been widely studied for industrial applications, such as sensors and temperature compensation devices. NTC thermistor thick films of <TEX>$Ni_{1+x}Mn_{2-x}O_{4+{\delta}}$</TEX> (x = 0.05, 0, -0.05) were fabricated on a glass substrate using the aerosol deposition method at room temperature. Resistance verse temperature (R-T) characteristics of the as-deposited films showed that the B constant ranged from 3900 to 4200 K between <TEX>$25^{\circ}C$</TEX> and <TEX>$85^{\circ}C$</TEX> without heat treatment. When the film was annealed at <TEX>$600^{\circ}C$</TEX> 1h, the resistivity of the film gradually decreased due to crystallization and grain growth. The resistivity and the activation energy of films annealed at <TEX>$600^{\circ}C$</TEX> for 1 h were 5.203, 5.95, and 4.772 <TEX>$K{\Omega}{\cdot}cm$</TEX> and 351, 326, and 299 meV for <TEX>$Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$</TEX>, <TEX>$NiMn_2O_4$</TEX>, and <TEX>$Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$</TEX>, respectively. The annealing process induced insulating <TEX>$Mn_2O_3$</TEX> in the Ni deficient <TEX>$Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$</TEX> composition resulting in large resistivity and activation energy. Meanwhile, excess Ni in <TEX>$Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$</TEX> suppressed the abnormal grain growth and changed <TEX>$Mn^{3+}$</TEX> to <TEX>$Mn^{4+}$</TEX>, giving lower resistivity and activation energy.

Preparation and characterization of Fe 3+-doped Ni 0.9Co 0.8Mn 1.3−xFe xO 4 (0 ≤ x ≤ 0.7) negative temperature coefficient ceramic materials

Based on spinel-type semiconducting electroceramics, negative temperature coefficient (NTC) thermistor materials, Ni 0.9Co 0.8Mn 1.3− x Fe x O 4 (0 ≤ x ≤ 0.7), with different compositions were synthesized by a co-precipitation method. The optimal pH value and the influence of Fe 3+ doping during the synthesis processing were discussed. As-prepared Ni 0.9Co 0.8Mn 1.3− x Fe x O 4 materials were characterized by DT/TGA, XRD, FTIR, SEM, electrical measurement and impendance analysis. It was found that, as the Fe doping content in the Ni 0.9Co 0.8Mn 1.3− x Fe x O 4 samples increased, both the grain size and the density decreased. The as-sintered Ni 0.9Co 0.8Mn 1.3− x Fe x O 4 samples presented a single-phase cubic spinel structure. The impendance diagram indicated that the grain boundary resistance was dominant in the overall impendance of Ni 0.9Co 0.8Mn 1.3− x Fe x O 4 NTC ceramic materials. The value of ρ 25, B 25/50, slope and activation energy for the samples Ni 0.9Co 0.8Mn 1.3− x Fe x O 4 sintered at 1200 °C were in the range of 453.1–2411 Ω cm, 3103–3355 K, 3.27325–3.43149 and 0.28207–0.29325 eV, respectively. This suggests that the electrical properties can be adjusted to desired values by controlling the Fe 3+ ion doping content.

Preparation and electrical properties of perovskite ceramics in the system BaBi 1− xSb xO 3 (0 ≤ x ≤ 0.5)

The effect of the composition on the electrical properties of BaBi 1− x Sb x O 3 (0 ≤ x ≤ 0.5) negative temperature coefficient (NTC) thermistors was studied. Major phases present in the sintered bodies of BaBi 1− x Sb x O 3 (0 < x < 0.5) ceramics were BaBi 0.5Sb 0.5O 3 compounds with a rhombohedral structure and BaBiO 3 compounds with a monoclinal structure. Most pores were located in the grains of BaBiO 3 and BaBi 0.5Sb 0.5O 3 ceramics. It was apparent that the ρ 25 and B 25/85 constant of the thermistors increased with increasing Sb content.

Structural and electrical properties of NiMgxMn2−xO4 NTC thermistors prepared by using sol–gel derived powders

Structure and electrical properties of NiMg x Mn 2− x O 4 (where x = 0, 0.1, 0.2, 0.3 and 0.4) ceramics prepared by using sol–gel derived powders have been studied. A careful control of the synthesis process enables producing NiMn 2 O 4 phase with spinel structure at a relatively low calcining temperature of 600 °C. All compositions showed a linear increase in ln ρ vs. 1/ T over the measured temperature range, indicative of negative temperature coefficient (NTC) characteristics. As the concentration of Mg increased from 0.0 to 0.4, the ρ 25 , B 25/85 stability constant and activation energy of NiMg x Mn 2− x O 4 thermistors increased from 4026 to 11,943 Ω cm, 3825–4144 K and 0.329–0.357 eV, respectively. In addition, the Δ R / R value first reduced fleetly from 0.78% to 0.32% and then decreased slowly to 0.12%.

Electrical properties and impedance analysis of Bi0.5Ba0.5FeO3 ceramic

Ba0.5Bi0.5FeO3 ceramic was fabricated by conventional solid-state reaction method. The microstructures and electrical properties were characterized by X-ray diffraction, scanning electron microscopy, direct current (DC) resistance-temperature measurement and alternative current (AC) impedance analysis. According to the analysis, Ba0.5Bi0.5FeO3 ceramic is a cubic perovskite-type compound, and its grain size is about 1.0 μm. In the measured temperature range of 16—280 ℃, Ba0.5Bi0.5FeO3 ceramic shows obvious negative temperature coefficient thermistor characteristic, and the thermistor constant and activation energy of the ceramic are 6490 K and 0.558 eV, respectively. The temperature dependence of dielectric constant reveals that below 280 ℃ no phase transition occurs. The AC impedance characteristic in the ceramic can appropriately be modeled in terms of an equivalent electrical circuit comprising of a series combination of three parallel RQ components in connection with the grain, grain shell and grain boundary effects. The fitting results are in good agreement with the experimental data. The components of grain, grain shell and grain boundary, showing NTC characteristic, have the order of resistive contribution of Rg&gt;Rs&gt;Rgb. In the temperature range 25—115 ℃, the significant mismatch between the peaks of parameters Z″(ω) (imaginary part of impedance) and M″(ω) (imaginary part of electric modulus) suggests a development of persistent localized conduction in Ba0.5Bi0.5FeO3 ceramic.

Electrical properties of lead-free thick film NTC thermistors based on perovskite-type BaCo IIxCo III2 xBi 1 − 3 xO 3

Lead-free thick film negative temperature coefficient (NTC) thermistors based on perovskite-type BaCo II x Co III 2 x Bi 1 − 3 x O 3 ( x ≤ 0.1) were prepared by mature screen-printing technology. The microstructures of the thick films sintered at 720 °C were examined by X-ray diffraction and scanning electron microscopy. The electrical properties were analyzed by measuring the resistance-temperature characteristics. For the BaBiO 3 thick films, the room-temperature resistivity is 0.22 MΩ cm, while the room-temperature resistivity is sharply decreased to about 3 Ω cm by replacing of Bi with a small amount of Co. For compositions 0.02 ≤ x ≤ 0.1, the values of room-temperature resistivity ( ρ 23), thermistor constant ( B 25/85) and activation energy are in the range of 1.995–2.975 Ω cm, 1140–1234 K and 0.102–0.111 eV, respectively.

Electrical properties of binder-free thick film BaY xBi 1− xO 3 NTC thermistors

The microstructure and electrical properties of BaY x Bi 1− x O 3 thick film negative temperature coefficient thermistors, fabricated by screen printing, were investigated. The sintered thick films were the single-phase solid solutions of the BaY x Bi 1− x O 3 compounds with a monoclinic structure. The added Y 2O 3 led to a significant decrease in the grain size of the thermistors. The resistivity and coefficient of temperature sensitivity for the BaY x Bi 1− x O 3 (0 ≤ x ≤ 0.15) thick film NTC thermistors decreased first with increasing x in the range of x < 0 .04 and then increased with further increase in x.