Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sinte...Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.展开更多
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...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(Sm_(0.2)Eu_(0.2)Gd_(0.2)Ho_(0.2)Yb_(0.2))CrO_(3)(HE-RECrO_(3))nanofibers were prepared by electro spinning.This work demonstrates that HE-RECrO_(3)nanofibe rs were successfully synthesized at a low temperature(800℃),which is approximately 400℃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-RECrO_(3)nanofibers decreases exponentially with increasing temperature from 25 to600℃.The logarithm of the resistivity is linearly related to the inverse of the temperature,confirming the negative temperature coefficient property of HE-RECrO_(3)nanofibers.The B_(25/50)value of the HERECrO_(3)nanofibers reaches 4072 K.In conclusion,HE-RECrO_(3)nanofibers are expected to be potential candidates for negative-temperature-coefficient(NTC)thermistors.展开更多
A mathematical method called Modifled Function Transformation Method(MFTM) for linearizing thermistors is proposed.Theoretically,the method has unified many schemes of linearizing thermistors into a mathematical ratio...A mathematical method called Modifled Function Transformation Method(MFTM) for linearizing thermistors is proposed.Theoretically,the method has unified many schemes of linearizing thermistors into a mathematical rational frame,and explained the reason of different circuits having the same capabilities for linearizing the thermistor characteristics.展开更多
A new type of miniature negative temperature coefficient (NTC) thermistors has been developed and manufactured with Mn-Ni-Cu-Fe oxides. The prepared NTC thermistors were calibrated in the temperature range from 77 K t...A new type of miniature negative temperature coefficient (NTC) thermistors has been developed and manufactured with Mn-Ni-Cu-Fe oxides. The prepared NTC thermistors were calibrated in the temperature range from 77 K to 300 K with 1 μA exciting currents. The automatic calibration apparatus as well as thermometric characteristics, stability, calibration equations and interchangeability of the manufactured thermistors were investigated. A mean fit equation was obtained: 1/<em>T</em> = 8.60 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> + 6.54 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> ln(<em>R/R</em><sub>ref</sub>) + 2.46 × 10<sup><span style="white-space:nowrap;">−</span>5</sup> ln(<em style="white-space:normal;">R/R</em><sub style="white-space:normal;">ref</sub>)<sup>2</sup> + 9.48 × 10<sup><span style="white-space:nowrap;">−</span>7</sup> ln(<em style="white-space:normal;">R/R</em><sub style="white-space:normal;">ref</sub>)<sup>3</sup> <span style="white-space:nowrap;">−</span> 2.16 × 10<sup><span style="white-space:nowrap;">−</span>8</sup> ln(<em style="white-space:normal;">R/R</em><sub style="white-space:normal;">ref</sub>)<sup>4</sup>. All the prepared NTC thermistors agreed with this fit with an error of 1.5 K. If the greater accuracy is required, a calibration is necessary, and the calibration accuracy is estimated to be ±10 mK.展开更多
Several complications of insertion and use of pulmonary artery catheter （PAC）, including catheter entrapment, are recognized during or after cardiac surgery. Early detection is very important. We report a case of PA...Several complications of insertion and use of pulmonary artery catheter （PAC）, including catheter entrapment, are recognized during or after cardiac surgery. Early detection is very important. We report a case of PAC entrapment because the the catheter was accidentally su- tured to the superior vena cava. Bleeding from the thermistor connector was initially detected after surgery because the needle punctured the lumen of thermistor connector. The PAC was removed through re-exploration. Therefore, bleeding from the thermistor connector could early indicate the PAC entrapment. We suggest that abnormal bleeding from the non-injectate lumen ports of PAC should be checked before sternal closure.展开更多
This paper is concerned with the superconvergence error estimates of a classical mixed finite element method for a nonlinear parabolic/elliptic coupled thermistor equations.The method is based on a popular combination...This paper is concerned with the superconvergence error estimates of a classical mixed finite element method for a nonlinear parabolic/elliptic coupled thermistor equations.The method is based on a popular combination of the lowest-order rectangular Raviart-Thomas mixed approximation for the electric potential/field(φ,θ)and the bilinear Lagrange approximation for temperature u.In terms of the special properties of these elements above,the superclose error estimates with order O(h^(2))are obtained firstly for all three components in such a strongly coupled system.Subsequently,the global superconvergence error estimates with order O(h^(2))are derived through a simple and effective interpolation post-processing technique.As by a product,optimal error estimates are acquired for potential/field and temperature in the order of O(h)and O(h^(2)),respectively.Finally,some numerical results are provided to confirm the theoretical analysis.展开更多
In the present study, Zn-doped CaTiO_3 nanocrystalline was synthesized to study the thermistor behavior with temperature. The X-ray powder diffraction analysis showed the formation of a single-phase orthorhombic struc...In the present study, Zn-doped CaTiO_3 nanocrystalline was synthesized to study the thermistor behavior with temperature. The X-ray powder diffraction analysis showed the formation of a single-phase orthorhombic structure at room temperature. The electrical resistance of the Zn-doped CaTiO_3 increased with increasing doping concentration and decreased at higher measuring temperature, showing a negative temperature coefficient of resistance(NTCR) behavior. Different thermistor parameters were calculated using Steinhart–Hart equations, whilst time domain analysis confirmed faster response towards applied voltage.展开更多
It is possible to fabricate highly sensitive NTCR(negative temperature coefficient of resistance)thermistor using nano crystalline CaTiO_(3) synthesized by high energy ball milling.Disc shaped green pellets were prepa...It is possible to fabricate highly sensitive NTCR(negative temperature coefficient of resistance)thermistor using nano crystalline CaTiO_(3) synthesized by high energy ball milling.Disc shaped green pellets were prepared and effects of sintering on the disc pellets were studied as thermistor by sintering the samples at 1000℃,1100℃and 1200℃.The as-prepared samples were characterized by X-ray diffraction(XRD),impedance analysis and electrical measurement.The resistivity of the prepared samples varies predictably with temperature:this makes them promising material for temperature sensor.The experimental results prove that nano crystalline CaTiO_(3) ceramic is one kind of thermistor with exponential negative temperature coefficient of resistance in the temperature range of 300-500℃.The samples have the advantages of rapid response,high sensitivity and capability to withstand thermal surges over the temperature range of 300-500℃.Resistance-temperature characteristics are described by thermistor equation with thermistor constant around 4003 K to 10795 K and thermal coefficient of resistanceαaround-1%/℃to-13%/℃.The activation energy is in the range of 0.34-0.93 eV.The observed thermistor parameters are found to be comparable with many of the known thermistor materials.This suggests that the electrical properties can be adjusted to desirable values by controlling the temperature parameter.The influence of fabrication process of disc thermistor and electrical properties are discussed.The study shows the potential of nano crystalline CaTiO_(3) to act as an NTCR material for thermistor applications.展开更多
The thermistor problem is a coupled system of nonlinear PDEs which consists of the heat equation with the Joule heating as a source, and the current conservation equation with temperature dependent electrical conducti...The thermistor problem is a coupled system of nonlinear PDEs which consists of the heat equation with the Joule heating as a source, and the current conservation equation with temperature dependent electrical conductivity. In this paper we make a numerical analysis of the nonsteady thermistor problem. L(infinity)(OMEGA), W1,infinity(OMEGA) stability and error bounds for a piecewise linear finite element approximation are given.展开更多
As functional materials, PTC thermistor ceramics characterized by a drastic increase in resistivity at its transition temperature have been widely used in high-technology areas such as temperature measurement and indi...As functional materials, PTC thermistor ceramics characterized by a drastic increase in resistivity at its transition temperature have been widely used in high-technology areas such as temperature measurement and indication, temperature control, protective switches and so on. At present, the PTC thermistors are fabricated by means of doping BaTiO<sub>3</sub> and their PTC effects result from the existence of acceptor state or electronic trap on grain boundary. But the fabrication process展开更多
Negative temperature coefficient(NTC)thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring.Although great progress has been achieved in NTC materials,enhan...Negative temperature coefficient(NTC)thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring.Although great progress has been achieved in NTC materials,enhancing sensitivity and maintaining this high sensitivity along with linearity across extensive temperature ranges remain a significant challenge.In this study,we introduce a diamondbased thermistor(DT)characterized by its outstanding sensitivity,swift response time,and broad temperature monitoring capabilities.The temperature constant B for this DT,measured from 30 to 300°C(B30/300),achieves an exceptional value of 8012 K,which notably exceeds the temperature sensing capabilities of previously reported NTC thermistors within this extensive range.Moreover,diamond’s unique thermal conductivity and stability significantly boost the response speed and durability of the DT,offering substantial advantages over traditional ceramic thermistors.The enhanced temperature-sensitive properties of the DT are attributed to the presence of impurity elements in polycrystalline diamond.Impedance analysis indicates a hopping conduction mechanism,likely involving C-H or C-N dipoles at the diamond grain boundaries.This study marks a significant leap forward in diamond thermistor technology and sheds light on the mechanisms of thermal active conduction in diamond materials.展开更多
A spherical thermistor, an accurate temperature sensor, is employed as an air velocity sensor in this work. The measuring principle is derived and the effects of the insulation layer, air temperature, natural convecti...A spherical thermistor, an accurate temperature sensor, is employed as an air velocity sensor in this work. The measuring principle is derived and the effects of the insulation layer, air temperature, natural convection and thermal radiation are discussed. Two different correlation relations for velocity measurements are proposed based on theoretical analyses and experimental calibrations. Experiments have shown that spherical thermistor is a good velocity sensor for speed between 0.1-2.5 m/s at room temperature and the insulation layer hardly influences the accuracy of the thermistor used in the present work. Modification on correlation can even further improve measurement accuracy. Since the thermistor is small and cheap, it is possible to apply this method to multi-point velocity measurement with a low disturbance to the flow field.展开更多
Y2O3-doped Zn1-xNixO (x=0,0.3,0.4,0.5,0.6,0.7,and 0.9) powders were prepared by a wet chemical synthesis method,and the related ceramics were obtained by the traditional ceramic sintering technology.The phases and rel...Y2O3-doped Zn1-xNixO (x=0,0.3,0.4,0.5,0.6,0.7,and 0.9) powders were prepared by a wet chemical synthesis method,and the related ceramics were obtained by the traditional ceramic sintering technology.The phases and related electrical properties of the ceramics were investigated.The analysis of X-ray diffraction (XRD) indicates that the prepared ceramics with Ni substitution have a cubic crystalline structure.The resistance-temperature feature indicates that all the ceramics show a typical effect of negative temperature coefficient (NTC) of resistivity with the thermal constants between 3998 and 5464 K,and have high cyclical stability in a temperature range from 25 to 300 ℃.The impedance analysis reveals that both grain effect and grain boundary effect contribute collectively to the NTC effect.The electron hopping and band conduction models are proposed for the grain (bulk) conduction,and the thermally activated charge carrier transport overcoming the energy barrier is suggested for the grain boundary conduction.展开更多
The effects of La_2O_3 doping on the phase structure.electric properties and aging properties of the samples were researched using XRD,SEM and electric property measurements.The results suggest that the aging value of...The effects of La_2O_3 doping on the phase structure.electric properties and aging properties of the samples were researched using XRD,SEM and electric property measurements.The results suggest that the aging value of Mn_(2.38)Ni_(0.5)Cu_(0.12)O_4 thermistor ceramic samples decreases from 10%to about 6%by only doping La_2O_3.The electrical stability of the sample has improved as well.Such doped material will broaden the production and application scope of Cu contained negative temperature coefficient thermal ceramics.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51302138 and 21663001)the Western Light Talent Training Program of Chinese Academy of Sciences。
文摘Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.
基金Project supported by the National Key Research and Development Program of China(2019YFC0605000)the"Transformational Technologies for Clean Energy and Demonstration",Strategic Priority Research Program of the Chinese Academy of Sciences(XDA21000000)+4 种基金the Independent Deployment Project of Ganjiang Innovation Research Institute of Chinese Academy of Sciences(E055A002)the Independent Deployment Project of China Fujian Innovation Laboratory of Optoelectronic Information Technology(2021ZZ109)the Fujian Provincial Natural Fund(2021J05101)the National Natural Science Foundation of China(21771196,62275276)Advanced Energy Science and Technology Guangdong Laboratory(HND20TDGFDC00)。
文摘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(Sm_(0.2)Eu_(0.2)Gd_(0.2)Ho_(0.2)Yb_(0.2))CrO_(3)(HE-RECrO_(3))nanofibers were prepared by electro spinning.This work demonstrates that HE-RECrO_(3)nanofibe rs were successfully synthesized at a low temperature(800℃),which is approximately 400℃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-RECrO_(3)nanofibers decreases exponentially with increasing temperature from 25 to600℃.The logarithm of the resistivity is linearly related to the inverse of the temperature,confirming the negative temperature coefficient property of HE-RECrO_(3)nanofibers.The B_(25/50)value of the HERECrO_(3)nanofibers reaches 4072 K.In conclusion,HE-RECrO_(3)nanofibers are expected to be potential candidates for negative-temperature-coefficient(NTC)thermistors.
文摘A mathematical method called Modifled Function Transformation Method(MFTM) for linearizing thermistors is proposed.Theoretically,the method has unified many schemes of linearizing thermistors into a mathematical rational frame,and explained the reason of different circuits having the same capabilities for linearizing the thermistor characteristics.
文摘A new type of miniature negative temperature coefficient (NTC) thermistors has been developed and manufactured with Mn-Ni-Cu-Fe oxides. The prepared NTC thermistors were calibrated in the temperature range from 77 K to 300 K with 1 μA exciting currents. The automatic calibration apparatus as well as thermometric characteristics, stability, calibration equations and interchangeability of the manufactured thermistors were investigated. A mean fit equation was obtained: 1/<em>T</em> = 8.60 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> + 6.54 × 10<sup><span style="white-space:nowrap;">−</span>4</sup> ln(<em>R/R</em><sub>ref</sub>) + 2.46 × 10<sup><span style="white-space:nowrap;">−</span>5</sup> ln(<em style="white-space:normal;">R/R</em><sub style="white-space:normal;">ref</sub>)<sup>2</sup> + 9.48 × 10<sup><span style="white-space:nowrap;">−</span>7</sup> ln(<em style="white-space:normal;">R/R</em><sub style="white-space:normal;">ref</sub>)<sup>3</sup> <span style="white-space:nowrap;">−</span> 2.16 × 10<sup><span style="white-space:nowrap;">−</span>8</sup> ln(<em style="white-space:normal;">R/R</em><sub style="white-space:normal;">ref</sub>)<sup>4</sup>. All the prepared NTC thermistors agreed with this fit with an error of 1.5 K. If the greater accuracy is required, a calibration is necessary, and the calibration accuracy is estimated to be ±10 mK.
基金supported by special research program, Ministry of Health, China (200902001)
文摘Several complications of insertion and use of pulmonary artery catheter （PAC）, including catheter entrapment, are recognized during or after cardiac surgery. Early detection is very important. We report a case of PAC entrapment because the the catheter was accidentally su- tured to the superior vena cava. Bleeding from the thermistor connector was initially detected after surgery because the needle punctured the lumen of thermistor connector. The PAC was removed through re-exploration. Therefore, bleeding from the thermistor connector could early indicate the PAC entrapment. We suggest that abnormal bleeding from the non-injectate lumen ports of PAC should be checked before sternal closure.
基金supported by the National Natural Science Foundation of China(Grant Nos.12101568,12071443).
文摘This paper is concerned with the superconvergence error estimates of a classical mixed finite element method for a nonlinear parabolic/elliptic coupled thermistor equations.The method is based on a popular combination of the lowest-order rectangular Raviart-Thomas mixed approximation for the electric potential/field(φ,θ)and the bilinear Lagrange approximation for temperature u.In terms of the special properties of these elements above,the superclose error estimates with order O(h^(2))are obtained firstly for all three components in such a strongly coupled system.Subsequently,the global superconvergence error estimates with order O(h^(2))are derived through a simple and effective interpolation post-processing technique.As by a product,optimal error estimates are acquired for potential/field and temperature in the order of O(h)and O(h^(2)),respectively.Finally,some numerical results are provided to confirm the theoretical analysis.
文摘In the present study, Zn-doped CaTiO_3 nanocrystalline was synthesized to study the thermistor behavior with temperature. The X-ray powder diffraction analysis showed the formation of a single-phase orthorhombic structure at room temperature. The electrical resistance of the Zn-doped CaTiO_3 increased with increasing doping concentration and decreased at higher measuring temperature, showing a negative temperature coefficient of resistance(NTCR) behavior. Different thermistor parameters were calculated using Steinhart–Hart equations, whilst time domain analysis confirmed faster response towards applied voltage.
文摘It is possible to fabricate highly sensitive NTCR(negative temperature coefficient of resistance)thermistor using nano crystalline CaTiO_(3) synthesized by high energy ball milling.Disc shaped green pellets were prepared and effects of sintering on the disc pellets were studied as thermistor by sintering the samples at 1000℃,1100℃and 1200℃.The as-prepared samples were characterized by X-ray diffraction(XRD),impedance analysis and electrical measurement.The resistivity of the prepared samples varies predictably with temperature:this makes them promising material for temperature sensor.The experimental results prove that nano crystalline CaTiO_(3) ceramic is one kind of thermistor with exponential negative temperature coefficient of resistance in the temperature range of 300-500℃.The samples have the advantages of rapid response,high sensitivity and capability to withstand thermal surges over the temperature range of 300-500℃.Resistance-temperature characteristics are described by thermistor equation with thermistor constant around 4003 K to 10795 K and thermal coefficient of resistanceαaround-1%/℃to-13%/℃.The activation energy is in the range of 0.34-0.93 eV.The observed thermistor parameters are found to be comparable with many of the known thermistor materials.This suggests that the electrical properties can be adjusted to desirable values by controlling the temperature parameter.The influence of fabrication process of disc thermistor and electrical properties are discussed.The study shows the potential of nano crystalline CaTiO_(3) to act as an NTCR material for thermistor applications.
文摘The thermistor problem is a coupled system of nonlinear PDEs which consists of the heat equation with the Joule heating as a source, and the current conservation equation with temperature dependent electrical conductivity. In this paper we make a numerical analysis of the nonsteady thermistor problem. L(infinity)(OMEGA), W1,infinity(OMEGA) stability and error bounds for a piecewise linear finite element approximation are given.
文摘As functional materials, PTC thermistor ceramics characterized by a drastic increase in resistivity at its transition temperature have been widely used in high-technology areas such as temperature measurement and indication, temperature control, protective switches and so on. At present, the PTC thermistors are fabricated by means of doping BaTiO<sub>3</sub> and their PTC effects result from the existence of acceptor state or electronic trap on grain boundary. But the fabrication process
基金supported by the Fundamental Research Funds for the Central Universities(CUG2106117)Hubei Jewelry Engineering Technology Research Center(CIGTXM03202301)+1 种基金Hubei Provincial Natural Science Foundation(20241350053)GuangDong Basic and Applied Basic Research Foundation(2023A1515110043).
文摘Negative temperature coefficient(NTC)thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring.Although great progress has been achieved in NTC materials,enhancing sensitivity and maintaining this high sensitivity along with linearity across extensive temperature ranges remain a significant challenge.In this study,we introduce a diamondbased thermistor(DT)characterized by its outstanding sensitivity,swift response time,and broad temperature monitoring capabilities.The temperature constant B for this DT,measured from 30 to 300°C(B30/300),achieves an exceptional value of 8012 K,which notably exceeds the temperature sensing capabilities of previously reported NTC thermistors within this extensive range.Moreover,diamond’s unique thermal conductivity and stability significantly boost the response speed and durability of the DT,offering substantial advantages over traditional ceramic thermistors.The enhanced temperature-sensitive properties of the DT are attributed to the presence of impurity elements in polycrystalline diamond.Impedance analysis indicates a hopping conduction mechanism,likely involving C-H or C-N dipoles at the diamond grain boundaries.This study marks a significant leap forward in diamond thermistor technology and sheds light on the mechanisms of thermal active conduction in diamond materials.
文摘A spherical thermistor, an accurate temperature sensor, is employed as an air velocity sensor in this work. The measuring principle is derived and the effects of the insulation layer, air temperature, natural convection and thermal radiation are discussed. Two different correlation relations for velocity measurements are proposed based on theoretical analyses and experimental calibrations. Experiments have shown that spherical thermistor is a good velocity sensor for speed between 0.1-2.5 m/s at room temperature and the insulation layer hardly influences the accuracy of the thermistor used in the present work. Modification on correlation can even further improve measurement accuracy. Since the thermistor is small and cheap, it is possible to apply this method to multi-point velocity measurement with a low disturbance to the flow field.
基金The authors acknowledge the financial support provided by the National Natural Science Foundation of China，the Laboratory Research Fund by the State Key Laboratory of Powder Metallurgy,Central South University,China
文摘Y2O3-doped Zn1-xNixO (x=0,0.3,0.4,0.5,0.6,0.7,and 0.9) powders were prepared by a wet chemical synthesis method,and the related ceramics were obtained by the traditional ceramic sintering technology.The phases and related electrical properties of the ceramics were investigated.The analysis of X-ray diffraction (XRD) indicates that the prepared ceramics with Ni substitution have a cubic crystalline structure.The resistance-temperature feature indicates that all the ceramics show a typical effect of negative temperature coefficient (NTC) of resistivity with the thermal constants between 3998 and 5464 K,and have high cyclical stability in a temperature range from 25 to 300 ℃.The impedance analysis reveals that both grain effect and grain boundary effect contribute collectively to the NTC effect.The electron hopping and band conduction models are proposed for the grain (bulk) conduction,and the thermally activated charge carrier transport overcoming the energy barrier is suggested for the grain boundary conduction.
文摘The effects of La_2O_3 doping on the phase structure.electric properties and aging properties of the samples were researched using XRD,SEM and electric property measurements.The results suggest that the aging value of Mn_(2.38)Ni_(0.5)Cu_(0.12)O_4 thermistor ceramic samples decreases from 10%to about 6%by only doping La_2O_3.The electrical stability of the sample has improved as well.Such doped material will broaden the production and application scope of Cu contained negative temperature coefficient thermal ceramics.
