ENERGY
·
2014
·
IF 4.159
Wen-long Cheng,Shuai Yuan,Jia-liang Song
PTC (positive temperature coefficient) material is a kind of thermo-sensitive material. In this study, a series of novel PTC materials adapted to thermal control of electron devices are prepared. By adding different low-melting-point blend matrixes into GP (graphite powder)/LDPE (low density polyethylene) composite, the Curie temperatures are adjusted to 9 °C, 25 °C, 34 °C and 41 °C, and the resistance–temperature coefficients are enhanced to 1.57/°C–2.15/°C. These PTC materials remain solid in the temperature region of PTC effect, which makes it possible to be used as heating element to achieve adaptive temperature control. In addition, the adaptive thermal control performances of this kind of materials are investigated both experimentally and theoretically. The result shows that the adaptive effect becomes more significant while the resistance–temperature coefficient increases. A critical heating power defined as the initial heating power which makes the equilibrium temperature reach terminal temperature is presented. The adaptive temperature control will be effective only if the initial power is below this value. The critical heating power is determined by the Curie temperature and resistance–temperature coefficient of PTC materials, and a higher Curie temperature or resistance–temperature coefficient will lead to a larger critical heating power.
研究领域:
材料科学
·
热力学工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Xiangxiang Zhu,Haishan Wang,Ruiting Hou,Junfeng Li,Yule Li,Qingming Chen,Hui Zhang
Novel Mn 3 O 4 - LaMnO 3 composite ceramics have been successfully designed by the Pechini sol-gel routine, ceramics were calcined at 1450 °C for 12 h in air, and the electrical properties of its negative temperature coefficient at room temperature (300K) were investigated. X-ray diffraction and SEM results indicate that all the samples consist of two phases, LaMnO 3 and Mn 3 O 4 , and illustrate highly crystalline quality. The electrical transport measurements show that the temperature coefficient of resistance (TCR) vs . temperature of the composite presents a ‘U’ shape at wide-temperature-range(188–350K), which is beneficial for the performance of practical devices. Low resistivity ρ and TCR revealed for pure LaMnO 3 , While TCR and room temperature range were increased with the addition of Mn 3 O 4 phase into LaMnO 3 . Enhanced electrical properties with moderate resistivity ρ make it a prominent and potential candidate to be utilized in portable, uncooled bolometer.
研究领域:
材料科学
·
电子工程
✓ 已验证
DOI
高影响因子
Materials
·
2019
·Vol. 12
·期 5
·803
·
IF 2.972
Lei Tian,Jing Nan,He Wang,Chunying Shen
Perovskite ceramics are a common microwave dielectric material, but the development and application of this material has been limited by the high, positive resonance frequency temperature coefficient and sintering temperature. Therefore, adjusting the temperature coefficient of the resonance frequency and reducing the sintering temperature have become important research directions. In this work, 0.95(Ca0.88Sr0.12)TiO3–0.05(Bi0.5Na0.5)TiO3ceramics (referred to as 0.95CST-0.05BNT) were prepared by standard solid-state reaction and microwave sintering. Microwave sintering greatly shortened the sintering period and holding time. Moreover, the 0.95CST–0.05BNT ceramics showed more uniform grain size distribution, and microwave sintering reduced energy consumption in the experiment. Therefore, the temperature coefficient of the resonance frequency of MWS ceramics was reduced by 119 × 10−6/℃. All of the ceramics, which were sintered at 1300 °C for 40 minutes, showed optimal microwave dielectric properties:εr= 187.6,Q×f= 8958 GHz, andτf= +520 × 10−6/°C.Keywords:dielectric properties;microwave sintering;temperature coefficient;ceramics
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Materials Today Communications
·
2022
·
IF 3.662
Zhouyao Yue,Huashan Wang,Xiurong Hou,Yuting Shi,Xin Zhang
Positive temperature coefficient (PTC) materials usually have NTC effect, and the effect is poor. In this paper, conductive carbon black (CB) and amorphous elastomer (TPO) were introduced into high-density polyethylene (HDPE) by melting mixing and hot pressing methods and treated with peroxide crosslinking to improve the PTC properties of conductive composites. The results show that the percolation threshold reduces from 24 wt% to 22 wt% for crosslinked elastic networks. At the same time, the room temperature resistance of the composite material does not show monotonicity after three cycles, which has good reproducibility and eliminates the NTC effect of the composite material. This work provides both a simple way to produce high-performance PTC materials and a new idea to improve the stability of PTC materials.
研究领域:
材料科学
·
高分子科学
·
电气工程
✓ 已验证
DOI
高影响因子
RARE METALS
·
2024
·
IF 9.6
Zeng Jin-Quan,Qi Jun-Lei,Yang Yue-Yang,Zhang Min-Hao,Lin Yuan-Hua
The practical application of CaSmAlO 4 microwave dielectric ceramics is limited by its low quality factor ( Q × f ) value and non-zero temperature coefficient resonant frequency ( τ f ) value. In this study, we introduced Mg 2+ –Ti 4+ ionic pairs into CaSmAlO 4 , along with an excess of 9% Sm 2 O 3 . The Mg 2+ –Ti 4+ ionic pairs substituted Al 3+ , and two phases simultaneously coexisted in the ceramics: CaSmAlO 4 and Sm 2 O 3 . As the doping concentration of Mg 2+ –Ti 4+ ionic pairs increased, the relative permittivity exhibited an upward trend, while the quality factor and resonant frequency temperature coefficient first rose and then descended. Remarkably, 0.09Sm 2 O 3 –0.91CaSmAl 0.7 Mg 0.15 –Ti 0.15 O 4 sintered at 1450 °C yielded excellent dielectric properties: ε r = 19.72, Q × f = 72,936 GHz, and τ f = –0.044 ppm·°C − 1 . The factors influencing the microwave dielectric properties of 0.09Sm 2 O 3 –0.91CaSmAlO 4 ceramics were further examined by considering the crystal structure, grain size, Lichtenecker logarithmic rule, tolerance factor and packing fraction. Graphic abstract
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
·
2024
·Vol. 110
·期 3
·678-689
·
IF 2.3
Hou Ruiting,Wang Shaozheng,Wang Haishan,Tian Lanlan,Zhu Xiangxiang,Li Yule,Chen Qingming,Zhang Hui
La 1- x Ca x MnO 3 , as a candidate for thermal radiation detectors, has received more attention due to the quest for a higher temperature coefficient of resistance (TCR), however, the narrow high-TCR temperature range greatly limits its application in uncooled bolometer. In this paper, Mn 3 O 4 - La 1- x Ca x MnO 3 ( x = 0–0.33) composite ceramics were prepared using the sol-gel method. A suitable TCR was achieved over a wide temperature range, including room temperature, by adjusting the Ca content. As the Ca content decreased, the resistivity ( ρ ) of the composite gradually increased at 300 K, and the positive TCR (PTC) peak shifted to a lower temperature. However, the negative TCR (NTC) was enhanced over a wider temperature range. When x = 0.05, the maximal NTC was −3.2%·K −1 within the range of 172 K–350 K and |TCR| > 2%·K −1 , spanning a large temperature range around 180 K, including room temperature. These results strongly indicate that the composite, such as Mn 3 O 4 - La 1- x Ca x MnO 3 , provides a new idea for uncooled bolometer/night vision. Graphical Abstract
研究领域:
材料科学
·
物理学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2011
·Vol. 95
·期 1
·37-40
·
IF 2.169
Songping Wu,Chan Jiang,Youxian Mei,Weiping Tu
The Sm 2 SiO 5 ceramics were synthesized and their microwave dielectric properties were investigated. The pure monoclinic Sm 2 SiO 5 phase could be obtained when the molar ratio of Sm 2 O 3 /SiO 2 was 1:1.05 at 1350°C. A small amount of hexagonal Sm 4 (SiO 4 ) 3 second phase occurred as temperature increased. The relative density of Sm 2 SiO 5 ceramics increased with increasing temperature. The Sm 2 SiO 5 ceramics sintered at 1500°C exhibited microwave dielectric properties: a dielectric constant (ε r ) of 8.44, a quality factor ( Q × f ) of 64 000 GHz, and a temperature coefficient of resonant frequency (τ f ) of −37 ppm/°C. The Sm 2 SiO 5 ceramics have a wide sintering temperature region and small negative τ f values. They are promising candidate materials for millimeter-wave devices.
研究领域:
材料科学
·
电子工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2019
·
IF 4.175
Weishuang Fang,Kai Cheng,Huicheng Xiang,Ying Tang,Yifan Zhai,Congxue Su,Liang Fang
It has become a focus to develop low-permittivity microwave dielectric materials to meet the needs of high-speed transmission in telecommunication devices. Here, we report two Ge-based microwave dielectric ceramics prepared using the conventional solid-state method, MgGeO 3 and ZnGeO 3 , with low permittivity of 6.8 and 6.6, the high-quality factor of 65,200 GHz and 25,200 GHz, and negative temperature coefficient of −45 ppm/°C and −35 ppm/°C. Orthorhombic ilmenite structure of MgGeO 3 can be obtained in the range of 1160–1240 °C. However, the single-phase ZnGeO 3 is not available in air, and the ceramics sintered at 1040–1120 °C contain two phases of Zn 2 GeO 4 and GeO 2 .
研究领域:
材料科学
·
电子工程
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Wengao Pan,Qingping Lin,Lili Xiao,Shihao Feng,Ying Li,Jie Gao,Pengfei Yue,Guoshang Zhang
Perovskite structural LiBaF 3 ceramics with excellent microwave dielectric properties were synthesized using traditional solid-state method. By regulating the sintering temperatures from 600 °C to 675 °C, LiBaF 3 ceramics exhibit tunable dielectric constant ( ε r ) from 12.42 to 13.72, adjustable Q × f value from 55000 GHz to 73000 GHz, and regulable temperature coefficient of resonance frequency ( τ f ) from −36.78 ppm/°C to −34.68 ppm/°C. The properties are strongly associated with the density, and can be further optimized by 0.5 wt%TiO 2 addition ( ε r = 14.43, Q × f = 56000 GHz, τ f = -1.26 ppm/°C). The LiBaF 3 ceramics also exhibit excellent compatibility with Ag and Al electrodes. Furthermore, relationships between multiscale structures and microwave dielectric properties of the ceramics were revealed. Oxidation behaviors between LiBaF 3 and O 2 would result in the lattice shrinkage, the introduction of defect level, the decrease of bandgap and density, and then deteriorating the microwave dielectric properties. All the findings make the LiBaF 3 ceramic a promising candidate for ULTCC application, and may facilitate the development of other novel microwave dielectric materials.
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2019
·Vol. 30
·期 21
·19598-19608
·
IF 2.195
Li Pengfei,Zhang Hong,Gao Caiyun,Jiang Guoxiang,Li Zhicheng
N egative temperature coefficient (NTC) ceramics based on simple ZnO were prepared and investigated in present work, where slight amount of Al- and La- ions were added as semiconductor dopants, and Cu-ions were selected as the sintering agent and property modificator. All the prepared ZnO-based ceramics have a wurtzite structure and show typical NTC characteristic. For various contents of Al-, La- and Cu- ions in ZnO-based ceramics, ρ 25 can be adjusted from 0.65 kΩ cm to 3.28 MΩ cm, and B values were obtained in range of 2500 K to 5850 K. The ageing treatment at 125 °C for 600 h in air revealed that the ZnO-based ceramics have high thermal stability with the resistance shift < 2%. The complex impedance spectra were applied to analyze the electrical performance.
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF LUMINESCENCE
·
2015
·
IF 2.719
Wenyan Liu,Yu Zhang,Jia Zhao,Yi Feng,Dan Wang,Tieqiang Zhang,Wenzhu Gao,Hairong Chu,Jingzhi Yin,Yiding Wang,Jun Zhao,William W. Yu
The enhanced photoluminescence (PL) for In-rich copper indium sulfide quantum dots (CIS QDs) was observed. The conduction electron-Cu vacancy recombination and the donor–acceptor pair (DAP) defect recombination were considered to exist in CIS QDs at the same time. The temperature-dependent PL study showed that the emission of these QDs might be mainly originated from the recombination between electrons in the quantized conduction band and holes in the copper vacancy acceptor when x was 0.500 (Cu x In 1− x S). However, the temperature coefficient of PL peak position decreased when x was 0.237. That meant the DAP recombination increased in the In-rich CIS QDs.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Huang Ming,Zhang Jinxian,Tang Yu,Mao Haijun,Liu Zhuofeng,Li Wei,Wang Fenglin,Zhang Weijun,Chen Xingyu
A novel MnTiNb 2 O 8 -based microwave dielectric ceramic was synthesized by solid-state route and its microwave dielectric properties were investigated. The effects of excess Mn 2+ on the microstructure and microwave dielectric properties of Mn x TiNb 2 O 8 ( x = 1.00–1.20) were investigated. The X-ray diffraction and scanning electron microscopy results showed that MnTiNb 2 O 8 was the dominant crystalline phase in all samples, but TiO 2 , as a second phase, was consistently present. The complex impedance spectroscopy and X-ray photoelectron spectroscopy analysis suggested that the addition of a small amount of Mn could inhibit the formation of oxygen vacancies and hinder the reduction of Ti 4+ . The study found that by adding a small amount of Mn, the quality factor ( Q × f ) of ceramics can be significantly improved without affecting the dielectric constant ( ε r ), thereby greatly optimizing the dielectric properties of ceramics. Subsequently, the temperature coefficient of resonant frequency ( τ f ) of the ceramic was successfully adjusted to near zero by adding a small amount of Zr 4+ instead of Ti 4+ . Among all Mn x Ti 1- y Zr y Nb 2 O 8 ( x = 1.00–1.20, 0 ≤ y ≤ 0.28) ceramics, samples with x = 1.05 and y = 0.1 sintered at 1200 °C showed the best microwave dielectric properties: ε r = 32.9, Q × f = 11,427 GHz, and τ f = 0 ppm/°C.
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）