Effects of Glass-Additives on the Properties of Ni/Ceramic PTC Composites

2007 ◽  
Vol 280-283 ◽  
pp. 337-340
Author(s):  
Yuan Fang Qu ◽  
Hua Tao Wang ◽  
Xiao Lei Li ◽  
Wei Bing Ma
Keyword(s):  
Contact Resistance ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Ceramic Composites ◽  
Room Temperature Resistivity ◽  
Sintering Aids ◽  
Ptc Effect ◽  
Suitable Amount ◽  
Interface Contact ◽  
Temperature Resistivity

The effects of glass additives on the sintering and properties of Ni/(Ba0.92Sr0.08)TiO3 composites were investigated. Due to the addition of glass additives, Ni/ceramic composites with low room-temperature resistivity and obvious PTC effect were obtained at a low sintering temperature. It was shown that glass-additives could form liquid phase that aided the solution and diffusion of solid atoms, acting as sintering aids to accelerate the sintering and lower the sintering temperature. The room-temperature resistivity decreased first and increased later with the increasing content of glassadditives, which was explained by two functions of glass-additives, decreasing interface contact resistance as sintering aids and adding volume resistance as insulators. Moreover, a suitable amount of glass-additives could enhance the PTC effect unexpectedly, which was attributed to the decrease of the contact resistance existing at the ceramic/ceramic interface.

Preparation of Ni/BaTiO3 Composites and PTC Effect

2007 ◽  
Vol 280-283 ◽  
pp. 341-344
Author(s):  
Xiao Lei Li ◽  
Yuan Fang Qu ◽  
Wei Bing Ma ◽  
Zhan Shen Zheng
Keyword(s):  
Heat Treatment ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Ptc Effect ◽  
Reducing Atmosphere ◽  
Prepared Composite ◽  
Temperature Resistivity ◽  
Ntc Effect

Ni/BaTiO3 composite was prepared by decomposition of NiC2O4·2H2O/BaTiO3 precursor, which was prepared by precipitating of nickel in the form of oxalate into the BaTiO3 slurry. The composite must be sintered in reducing atmosphere. Otherwise NTC effect would be introduced. The prepared composite almost had no PTC effect. But PTC effect of the Ni/BaTiO3 composite can be effectively renewed by heat-treatment in air. Under a proper composition and method, the composite shows low room-temperature resistivity (ρRT=6.0 Ω·cm) and obvious PTC effect (ρmax/ρmin=102).

Quantitative calculation of barium vacancy formation mechanism effects on the room-temperature resistance and PTCR effect in donor-doped BaTiO3 ceramics

2016 ◽  
Vol 30 (27) ◽  
pp. 1650211
Author(s):  
Chao Fang
Keyword(s):  
Formation Mechanism ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Positive Temperature Coefficient ◽  
Vacancy Formation ◽  
Room Temperature Resistivity ◽  
Positive Temperature ◽  
Quantitative Calculation ◽  
Ptcr Effect ◽  
Temperature Resistivity

A modified barium vacancy formation mechanism in donor-doped barium titanate (BaTiO3) ceramics is proposed. Assuming a uniform distribution of barium vacancies at sintering temperature and only oxygen partial pressure and sintering temperature related concentration of unionized barium vacancies, the electrical characteristics have been calculated by solving a differential equation about electron level. The room-temperature resistivity and positive temperature coefficient of resistivity (PTCR) behaviors of donor-doped BaTiO3 semiconducting ceramics have been quantitatively computed. The results pointed out that the room-temperature resistivity changes as a U-type curve with an increase of donor concentration. Moreover, the PTCR effect of BaTiO3 semiconductive ceramics was calculated quantitatively under different conditions. Theoretical and experimental results for BaTiO3 semiconductive ceramics are compared and discussed.

Effect of processing parameters on the characteristics of high-Tc superconductor YBa2Cu3Oy

1988 ◽  
Vol 3 (6) ◽  
pp. 1304-1310 ◽  
Author(s):  
Narottam P. Bansal
Keyword(s):  
Room Temperature ◽  
High Temperature Superconductor ◽  
Sintering Temperature ◽  
Processing Parameters ◽  
Room Temperature Resistivity ◽  
Transition Width ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
Temperature Resistivity

The influence of sintering temperature, sintering and annealing atmospheres, and quench rate on the properties of the high-temperature superconductor YBa2Cu3Oy has been investigated by electrical resistivity and magnetic susceptibility measurements, thermogravimetric analysis, powder x-ray diffraction, and scanning electron microscopy. Room-temperature resistivity and the transition width decreased, and the fraction of the superconducting material and the bulk density increased with increase in the sintering temperature, but had no effect on the transition temperature (Tc) for samples fired in flowing oxygen. A sample that was rapidly quenched from 930 °C to room temperature after sintering in air had a perovskite structure and Tc (onset) ∼90 K but its resistance did not become zero even at 77 K. A sample sintered in air at 930 °C and furnace cooled had Tc (midpoint) of ∼89.6 K and transition width (10%–90%) of ∼2.6 K. The loss and gain of oxygen occurs reversibly in YBa2Cu3Oy.

The Influence of Donor-Doped Content on PTC Effect of Ba-Excess BaTiO3 Based Ceramics Fired in Reducing Atmosphere

2014 ◽  
Vol 1015 ◽  
pp. 425-429
Author(s):  
Xu Xin Cheng ◽  
Hai Ning Cui ◽  
Dong Xiang Zhou ◽  
Qiu Yun Fu
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Ptc Effect ◽  
Reducing Atmosphere ◽  
Donor Dopant ◽  
Temperature Resistivity

We investigated the influence of the Sm-doped contentration on the electrical properties and PTC effect of Ba-excess BaTiO3Based Ceramics, which were fired at 1300 °C for 30 min in a reducing atmosphere and then reoxidized at 850 °C for 1 h. The results showed that the donor dopant affected PTC characteristics and the electrical properties of the BSMT ceramics, whose room temperature resistivity first decreased and then increased with an increase in the Sm3+-doped content across the range from 0.1 to 0.5 mol%. The BSMT specimens exhibited a remarkable PTC effect, with a resistance jump greater by 2.7 orders of magnitude, along with a low room temperature resistivity of 128.6 Ω∙cm at the donor-doped content of 0.3 mol%. The influence of the donor dopant on the grain size of the as-fired samples has been also investigated.

The Influence of Donor-Doped Concentration on the PTCR Characteristics of the Ban-xSmxTiO3 Based Ceramics Sintered in Reducing Atmosphere

2014 ◽  
Vol 881-883 ◽  
pp. 1031-1034
Author(s):  
Xu Xin Cheng ◽  
Dong Xiang Zhou ◽  
Zhao Xiong Zhao ◽  
Qiu Yun Fu
Keyword(s):  
Electrical Properties ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Positive Temperature Coefficient ◽  
Room Temperature Resistivity ◽  
Positive Temperature ◽  
Reducing Atmosphere ◽  
Ptcr Effect ◽  
Temperature Coefficient Of Resistivity ◽  
Temperature Resistivity

Positive temperature coefficient of resistivity (PTCR) effect and electrical properties of (Ban-xSmx)TiO3(BSMT ) samples with different Ba-site/Ti-site ratio (n) and various concentration of the donor-doped Sm3+(x) sintered in a reducing atmosphere and reoxidized in air are investigated. The results show that the room temperature resistivity (ρRT) of the semiconducting BSMT ceramics first decreases and then increases with increasing of concentration of the donor-doped Sm3+, especially whenxis 0.005 mol, the ρRTof the BSMT ceramics is the lowest. Moreover, the ρRTof the Ba-excess BSMT (n= 1.01) specimens reoxidized at 800 oC for 1 h after sintering at 1270 °C for 30 min in a reducing atmosphere is lower than the Ti-excess ones (n= 0.99), in addition, the ρRTof the BSMT specimens increases with an increase of both sintering temperature and reoxidized time.

Influence of Modulation Wavelength Induced Order on the Physical Properties of Nb/Rare Earth Superlattices

1984 ◽  
Vol 37 ◽  
Author(s):  
L. H. Greene ◽  
W. L. Feldmann ◽  
J. M. Rowell ◽  
B. Batlogg ◽  
R. Hull ◽  
...  
Keyword(s):  
Rare Earth ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Residual Resistance ◽  
Sapphire Substrates ◽  
Transmission Electron ◽  
Sputter Deposited ◽  
Residual Resistance Ratio ◽  
Temperature Resistivity ◽  
Modulation Wavelength

AbstractWe report the observation of a higher degree of preferred crystalline orientation in Nb/rare earth superlattices for modulation wavelengths in the range of 200 Å to 500 Å than that exhibited by single component films. All films and multilayers are sputter deposited onto room temperature sapphire substrates. Electronic transport measurements also show that the residual resistance ratio is higher and the room temperature resistivity is lower than for multilayers of either greater or lower periodicities. Transmission electron micrographs (TEM) showing excellent layering, grain size comparable to the layer thickness, and evidence of some degree of epitaxy are presented.

scholarly journals Computational Intelligence Approach for Estimating Superconducting Transition Temperature of Disordered MgB2Superconductors Using Room Temperature Resistivity

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Taoreed O. Owolabi ◽  
Kabiru O. Akande ◽  
Sunday O. Olatunji
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Room Temperature ◽  
Optimization Technique ◽  
Support Vector ◽  
Measuring Instruments ◽  
Room Temperature Resistivity ◽  
Superconducting Transition ◽  
Experimental Values ◽  
Temperature Resistivity

Doping and fabrication conditions bring about disorder in MgB2superconductor and further influence its room temperature resistivity as well as its superconducting transition temperature (TC). Existence of a model that directly estimatesTCof any doped MgB2superconductor from the room temperature resistivity would have immense significance since room temperature resistivity is easily measured using conventional resistivity measuring instrument and the experimental measurement ofTCwastes valuable resources and is confined to low temperature regime. This work develops a model, superconducting transition temperature estimator (STTE), that directly estimatesTCof disordered MgB2superconductors using room temperature resistivity as input to the model. STTE was developed through training and testing support vector regression (SVR) with ten experimental values of room temperature resistivity and their correspondingTCusing the best performance parameters obtained through test-set cross validation optimization technique. The developed STTE was used to estimateTCof different disordered MgB2superconductors and the obtained results show excellent agreement with the reported experimental data. STTE can therefore be incorporated into resistivity measuring instruments for quick and direct estimation ofTCof disordered MgB2superconductors with high degree of accuracy.

The Influence of Sintering Atmosphere and Reoxidation Temperature on the Electrical Properties of the Chip-Type Ba1-xSmxTiO3 Based Ceramics

2014 ◽  
Vol 900 ◽  
pp. 134-137
Author(s):  
Xu Xin Cheng ◽  
Dong Xiang Zhou ◽  
Qi Jun Xiao ◽  
Zhao Xiong Zhao
Keyword(s):  
Electrical Properties ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Sintering Atmosphere ◽  
Reducing Atmosphere ◽  
Chip Type ◽  
Ptcr Effect ◽  
Temperature Resistivity

The PTCR characteristics of (Ba1-xSmx)TiO3(BSMT) with different donor-doped concentration (x) sintered in a reducing atmosphere and reoxidized in air are investigated. The results reveal that the room temperature resistivity (ρRT) of the semiconducting BSMT ceramics first decreases and then increases with increasing of thexvalues, especially whenxis 0.004, the semiconducting BSMT ceramics reoxidized at 850oC for 1 h after sintering at 1300 °C for 30 min in a reducing atmosphere achieve a lower room temperature resisitivity of 82.6 Ωcm. in addition, the doped 0.1 mol% Sm3+BSMT samples fired at 1300 °C for 30 min in air exhibit remarkable PTCR effect with a resistance jumping ratio of 3.4 orders magnitude; moreover, a lower ρRTof the BSMT specimens sintered in a reducing atmosphere is obtained.

Transport Studies in Single-Crystal Films of Cosi2 and Nisi2

1983 ◽  
Vol 25 ◽  
Author(s):  
J. C. Hensel ◽  
R. T. Tung ◽  
J. M. Poate ◽  
F. C. Unterwald ◽  
D. C. Jacobson
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Transport Studies ◽  
Single Crystal Films ◽  
Crystal Films ◽  
The Difference ◽  
Temperature Resistivity

ABSTRACTTransport studies have been performed on thin films of CoSi 2 and NiSis2 in the temperature range 1 to 300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiesen's rule is obeyed over a remarkable range of bombardment doses.

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