NTC Thermistor Research Articles

Effect on Structural, Electrical and Temperature Sensing behavior of Neodymium Doped Bismuth Ferrite

Synthesis of polycrystalline samples of Bi1-xNdxFeO3 [x = 0.5, 0.6, 0.7 and 0.8] were demonstrated following solid-state reaction method at high temperature. The structural properties of the sample were confirmed through the X-ray diffraction technique. The dielectric study of the compounds was performed at different frequencies in the range of 100 Hz – 10 6 Hz for various temperatures. The non-Debye type of relaxation process confirmed from impedance analysis. The materials showed a negative temperature coefficient of resistance (NTCR) behavior at various temperatures and frequencies. AC conductivity of the materials with frequency at different temperatures satisfied the universal power law of Johnscher. Thermistor constant (β), sensitivity factor (α), and stability factor for all the samples were calculated and confirmed the characteristics of NTC thermistor.

Cofiring of LTCC multilayer assemblies with integrated NTC thermistor temperature sensor layers

We have studied the integration of Ni–Co–Zn–Mn spinel NTC thermistor layers into LTCC multilayer modules. Sintering of the cubic spinel Ni0.5Co0.5Zn0.75Mn1.25O4 with addition of 3 wt% Bi2O3 additive at 900 °C resulted in samples with 96% density and with good electrical performance. Thermistor spinel tapes, fabricated using doctor blade tape casting, were stacked with layers of a commercially available low-k dielectric LTCC tape, and cofired at 900 °C. Free or constrained cofiring did not give crack-free multilayer samples. Thermistor layers were then integrated combining the commercial LTCC tape with a Zn titanate-based tape in one multilayer laminate, and error-free multilayer samples with a room-temperature resistivity of ρ298 = (2,9 ± 0.08) kΩcm and a thermistor constant of B = (4280 ± 200) K were obtained. This demonstrates the possibility of cofiring of functional ceramic and low-k LTCC tapes and shows the potential of NTC spinel thermistor layers as temperature sensors integrated in complex LTCC multilayer architectures.

A low-cost PCR instrument for molecular disease diagnostics based on customized printed circuit board heaters.

This article describes the fabrication of a low-cost Polymerase Chain Reaction (PCR) instrument to detect diseases. In order to reduce the instrument price and simplify construction we developed an alternative fabrication process, transforming conventional printed circuit boards (PCB) in heating elements, avoiding the use of aluminum heating/cooling blocks and Peltier devices. To cool down the reaction a simple computer fan was used. The vial holder was fabricated using two double side PCB boards assembled in a sandwich-like configuration. The bottom PCB has a resistance of 0.9 Ω used to heat the reaction mix, while the top layer has a resistance of 1.1 Ω to heat the vial body, preventing vapor condensation. The top board was maintained at ~ 110 ± 1°C during all cycles. The final device was able to heat and cool down the reaction at rates of ~ 2.0°C/s, a rate comparable to commercial thermocyclers. An SMD NTC thermistor was used as temperature sensors, and a PID (proportional-integral-derivative) control algorithm was implemented to acquire and precisely control the temperature. We also discuss how the instrument is calibrated. The device was tested successfully for the amplification of T. pallidum (Syphilis) bacterial DNA and Zika virus RNA samples, showing similar performance to a commercial PCR instrument.

Ignition and safety characteristics of semiconductor bridge with NTC thermistor

Ignition and safety characteristics of semiconductor bridge with NTC thermistor

Low-temperature sintered Ni\u2013Zn\u2013Co\u2013Mn\u2013O spinel oxide ceramics for multilayer NTC thermistors

The phase formation, sintering behavior and electrical properties of Ni–Co–Zn–Mn spinel NTC thermistor ceramics of the series Ni0.5ZnzCo0.5Mn2−zO4 with 0 ≤ z ≤ 1 were studied. In contrast to NiMn2O4, which exhibits limited stability in air below 730 °C and above 970 °C, the Zn–Co-substituted nickel manganite spinels are stable at T < 730 °C and decompose at Td > 900 °C, with Td increasing with decreasing Zn Content z. The samples were sintered at 900 °C with addition of 3 wt% Bi2O3 as sintering aid and densities of above 92% were achieved. The room temperature resistivity and thermistor B-constants are almost independent of composition at 0 ≤ z ≤ 0.6 and start to increase at higher Zn concentrations. A multilayer NTC thermistor was fabricated using green tapes of a spinel of composition z = 0.75, commercial Ag paste, and cofiring at 900 °C. The firing behavior, microstructure formation and electrical properties of the multilayer thermistor are reported.

NTC thermistor nonlinearity compensation using wheatstone bridge and novel dual-stage single-flash piecewise-linear ADC

NTC thermistor nonlinearity compensation using wheatstone bridge and novel dual-stage single-flash piecewise-linear ADC

LaCr0.7Fe0.3O3-NiMn2O4 supported NTC composite ceramics with a sandwich-like structure

A novel sandwich-like structure was first proposed to adjust the electrical properties of NTC thermistors. The LaCr0.7Fe0.3O3-NiMn2O4 supported composite ceramics with sandwich-like structure were initially fabricated via traditional solid-state reaction and uniaxial pressing methods, which allowed for the advantages of each component to be integrated into one material. X-Ray diffraction analysis indicates the ceramics mainly consisting of orthorhombic perovskite LaCr0.7Fe0.3O3 and cubic spinel NiMn2O4 phases. SEM images manifest that the three layers adhered well to each other and exhibited high density. For electrical properties, the ρ25°C was expanded to a wide range of 1182–110,233 Ω∙cm and could be adjusted to the desired values by tuning the volume ratio of two basic layers, the B value was enhanced from 3358 K to 4167 K by NiMn2O4, and the thermal stability was improved by LaCr0.7Fe0.3O3 with a resistance shift less than 0.55 % after annealing at 150 °C for 1500 h.

Synthesis of NTC thermistors with screen printing method from natural yarosite minerals

NTC thermistors can make from a mixture of metal oxides. Fe2O3 is a metal oxide contained up to 93.80% in the natural yarosite mineral and has the potential to be used as a material for making thermistors. The objective of this research is to use Fe2O3 from yarosite and Fe2O3 from imports in the production of NTC thermistor and to determine the effect of adding ZrO2 to a mixture of Fe2O3 from yarosite, ZnO and CuO in the manufacture of thick-film oxide ceramic NTC thermistors. Oxide ceramic powder is synthesized, using the sol-gel method. Furthermore, oxide ceramic powder was made into thick-film oxide ceramics made by screen printing technique with a sintering temperature of 1100°C for 2 hours, then characterized using XRD and SEM. After a thick-film oxide ceramic was coated, with silver paste, an NTC thermistor was obtained and measured its electrical resistance to temperature using a multimeter and temperature controller. The results of the analysis of XRD characterization reveal that the crystal system of the ceramic mixture from the samples was rhombohedral. Based on the results of SEM analysis, the addition of ZrO2 doping showed a change in grain size to be smaller. NTC thermistors with raw materials Fe2O3 from yarosite, ZnO, and CuO (Sample I) have resistance which decreases with increasing temperature according to the characteristics of NTC thermistors and has better electrical characteristic than Fe2O3 from imports, ZnO, and CuO (Sample III) for NTC thermistor applications that are preferred commercially. The addition of ZrO2 doping (Sample II) increases the resistance.

Structural and electrical properties of Ca-doped Co1.5−xCaxMn1.2Ni0.3O4 (0 ≤ x ≤ 0.8) NTC ceramics

The influence of Ca content on the morphology and related electrical properties of Co1.5−xCaxMn1.2Ni0.3O4 (x = 0, 0.2, 0.4, 0.8) ceramics was studied. Appropriate addition of Ca will reduce the grain size, but when the content of Ca is 0.4, the holes will appear on the surface. As the Ca content of Co1.5−xCaxMn1.2Ni0.3O4 increases from 0 to 0.8, the temperature-dependent resistivity (ρ25) decreases from 1291.5 to 180.8 Ω cm, and the value of B25/50 decreases from 3860 to 3077 K. This is because the addition of Ca ions promotes the valence conversion of Mn3+ ions to Mn4+ ions, reduces the ratio of Mn3+/Mn4+, and thereby reduces the resistivity. The results show that when the Ca content is 0.4, the material has small grain size, low resistivity, and B value. It can be used as a NTC thermistor potential candidate materials in the temperature range of 223 K to 323 K.

Preparation of Fe0.8Mn1.54Ni0.66O4 Nano-Ceramics by Sol-gel auto combustion and N2 Annealing for High Reliable NTC Thermistor

Fe0.8Mn1.54Ni0.66O4 nano-ceramics have been successfully prepared by sol-gel auto combustion. The microstructure and phase of these samples was observed by using Scanning Electron Microscopy and X-Ray Diffraction. The diameters of Fe0.8Mn1.54Ni0.66O4 ceramic particles pre-fired at 800℃ range from 52 to 83nm. The powder sintered at above 1050℃ has the compact and uniform spinel structure. We have investigated the electrical characteristics of these thermistors at different sintering temperatures and concluded that the sample sintered at 1200℃ is sufficient to form the appropriate spinel phase. Moreover, the thermistor annealed for 72h at 450~550℃ in N2 atmosphere has the drift value of &lt;0.7%.

The Simulation Study on Internal Stress in Multilayer Thermistors during Soldering Process

A new 3D finite element model to characterize the residual stress distribution in multilayer NTC thermistor during soldering process has been developed. During the soldering process, the effects of inner silver electrode number and lateral margin length on mechanical residual stress are studied. Throughout the weldbonding and heating process, the maximum and minimum principal stresses in the active region of the thermistor ceramic are not zero, which implies that most of the thermistor ceramic is not stress-free. Numerical results show that the increasing of the lateral margin length could effectively decrese the maximum tensile stress.

Improving the stability of Fe0.8Mn1.54Ni0.66O4 NTC thermistor with nano-powders and N2 annealing

Fe0.8Mn1.54Ni0.66O4 nano-ceramics have been successfully prepared by sol-gel auto combustion. The microstructure and phase of these samples were observed by using SEM and XRD. The diameters of Fe0.8Mn1.54Ni0.66O4 ceramic particles pre-fired at 800 °C range from 52 to 83 nm. The powder sintered at above 1050 °C has the compact and uniform spinel structure. We have investigated the electrical characteristics of these thermistors at different sintering temperatures and concluded that the sample sintered at 1200 °C is sufficient to form the appropriate spinel phase. Moreover, the thermistor annealed for 72 h at 450 ∼ 550 °C in N2 atmosphere has the drift rate of <0.7%.

Resistance-Temperature Characteristics of Cr Doped Ni&lt;sub&gt;0.7&lt;/sub&gt;Mn&lt;sub&gt;2-x&lt;/sub&gt;Cu&lt;sub&gt;0.3&lt;/sub&gt;Cr&lt;sub&gt;x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; NTC Thermistors

Manganese-based solid solution ceramics of transition metal with spinel-type crystal structure have generated much interest as NTC thermistors in various domestic and industrial applications. Doping has been considered as one of the most important method to improve their electrical properties. In this work, Cr doped Mn-based solid solution NTC ceramics Ni0.7Mn2-xCu0.3CrxO4 (x = 0.1, 0.2, 0.3 and 0.4) were prepared by solid-state reaction method. X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS) were applied to study the phase structure, surface morphology and surface element content. The results indicate that the resistance and B value increase as the substituted Cr content increases.

LaCr1-xFexO3 (0≤x≤0.7): A novel NTC ceramic with high stability

Perovskite-phase LaCr1-xFexO3 (0 ≤ x ≤ 0.7) ceramics were fabricated by two-step sintering of powders synthesized by conventional solid-state reaction. XRD patterns reveals that the ceramics are single-phased LaCr1-xFexO3 solid solution at lower Fe contents, but form a biphasic mixture of LaCrO3-LaFeO3 at higher Fe contents. SEM analysis indicates that Fe doping causes a reduction in porosity, and a corresponding increase in density. The effects of Fe doping on electrical properties have also been investigated. The electrical resistivity ρ25°C decreases initially and then increases within a wide range of 634.4–83915.9 Ω·cm with increasing Fe content, whereas B varies within a relatively narrow range of 3651−4301 K. Such combination enables it to be a potential candidate for NTC thermistors. An investigation of elevated-temperature aging behavior shows that the resistance shifts at 25 °C were less than 0.65 % after annealing at 125 °C in air for 1000 h, revealing that the material exhibits excellent stability.

Temperature-Dependent Electrical Characteristics of Disc-Shaped Compacts Fabricated using Calcined Eggshell Nano Powder and Dry Cassava Starch

Abstract Disc-shaped compacts were fabricated from two mix proportions of calcined eggshell nanopowder and dry cassava starch and then used as test samples. The electrical resistance (R), thermal sensitivity index (β) and electronic activation energy (Ea) of the samples measured over a temperature range from 35 to 75oC were found to decrease non-linearly in values with increasing temperature. It was also observed that the results obtained (R = 3.691E6 Ω – 6.210E7 Ω, β = 3812K – 5316K and Ea = 0.33 eV – 0.46 eV) fulfill market requirements by comparing very well with the established values for NTC thermistors. Hence, from manufacturing viewpoint, recycling of chicken eggshell wastes and cassava effluents can avail electronic industry with promising and alternative materials for fabrication of temperature sensing / monitoring / control devices suitable for engineering applications. This will also help to reduce environmental pollution.

A Real Time Linearization of NTC Thermistor using Hybrid Neuro-Fuzzy Logic based on VLSI Technology

A Real Time Linearization of NTC Thermistor using Hybrid Neuro-Fuzzy Logic based on VLSI Technology

The effects on residual stress in multilayer NTC thermistors during soldering process and bending test (I. soldering process)

A new three-dimensional finite element model to characterize the residual stress distribution in multilayer NTC thermistor during soldering process has been developed. During the soldering process, the effects of inner silver electrode number and lateral margin length on mechanical residual stress are studied. Throughout the weldbonding and heating process, the maximum and minimum principal stresses in the active region of the thermistor ceramic are not zero, which implies that most of the thermistor ceramic is not stress-free. Numerical results show that the increasing of the lateral margin length could effectively decrease the maximum tensile stress.

A 16.1-bit Resolution 0.064-mm2 Compact Highly Digital Closed-Loop Single-VCO-Based 1-1 Sturdy-MASH Resistance-to-Digital Converter With High Robustness in 180-nm CMOS

A novel direct resistive-sensor-to-digital readout circuit is presented, which achieves 16.1-bit ENOB while being very compact and robust. The highly digital time-based architecture employs a single voltage-controlled oscillator (VCO), counter, and digital feedback loop for the readout of an external single-ended highly nonlinear resistive sensor, such as an NTC thermistor. In addition to the inherent first-order noise shaping due to the oscillator, the second loop in SMASH configuration creates second-order noise shaping. Fabricated in 180-nm CMOS, the readout circuit achieves 16.1 bit of resolution for 1-ms conversion time and consumes only $171~\mu \text{W}$ , resulting in an excellent 2.4-pJ/c.s. FOMW for a resistive sensor interface while occupying only 0.064 mm 2. The specific closed-loop architecture tackles the VCO nonlinearity, achieving more than 14 bits of linearity. Multiple prototype chip samples have been measured in a temperature-controlled environment from −40 °C to 125 °C for the readout of commercial external NTC thermistors. A maximum temperature inaccuracy of 0.3 °C is achieved with only one-point trimming at room temperature. Since the circuit architecture decouples the sensor excitation from the feedback, high electromagnetic interference (EMI) immunity at the sensor node is demonstrated as well.

Characterization of Al-doped Mn–Co–Ni–O NTC thermistor films prepared by the magnetron co-sputtering approach

Abstract A serial of Al-doped Mn–Co–Ni–O thermistor thin films were prepared by a magnetron co-sputtering system using an Mn1.4Co1.3Ni0.3 alloy target and an Al target. The composition and electrical properties of the thin films could be well controlled by adjusting the sputtering power of the Al target. It was found that the Mn3+, Mn4+, and Co2+ cations at the octahedral sites of the compact and flat films were gradually replaced by the Al3+ cation during doping. The amount of Al dopant in the compound film was easily adjusted by controlling the sputtering power applied to the doping Al target. The experimental results demonstrate that the NTC characters were found in all films. The optimum point (15 W) of Al sputtering power was determined, at which both the maximum material constant B value (4112 K) and the lowest carrier concentration (2.46 × 1014 cm−3) was characterized in the film. The significant enhancement of the B value for NTC thin films can potentially widen the temperature measurement range for sensing applications.

Design and Application of High-Precision Temperature Measuring Instrument for Ice Cover Profile of River Based on the Resistance Residual Compensation Method

Based on the temperature characteristics of the air, ice and water in the vertical direction of the river ice cover, an automatic temperature measuring instrument for ice cover profile was designed. The sensor used NTC thermistor as a temperature detection unit. In order to improve the actual detection accuracy of the sensor units in a wide temperature range [223.15 K (-50°C), 293.15 K (20°C)], a calibrating method of the thermistor using the resistance residual compensation method was proposed and compared with the existing seven calibration methods. The results show that the accuracy of the calibrated temperature sensor units can reach 0.1 K in the testing range, which can satisfy the accuracy requirements in thermodynamics research of ice cover profile. We further designed a temperature measuring instrument and carried out a deployment of the instrument and in-situ observation of data in cold region of the upstream of Heilongjiang River in late December 2017. The evolution process of ice thickness was analysed and discussed by the collected data. It can be proved that this instrument is an effective scheme for intelligent detection of river ice environment in cold regions.