scholarly journals Low-temperature sintered Ni–Zn–Co–Mn–O spinel oxide ceramics for multilayer NTC thermistors

2021 ◽  
Author(s):  
Timmy Reimann ◽  
Jörg Töpfer
Keyword(s):  
Electrical Properties ◽  
Room Temperature ◽  
Sintering Behavior ◽  
Room Temperature Resistivity ◽  
Oxide Ceramics ◽  
Sintering Aid ◽  
Zn Content ◽  
Ntc Thermistor ◽  
Ag Paste ◽  
Temperature Resistivity

AbstractThe 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.

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.

Characterization of 6H-SiC Single Crystals Grown by PVT Method Using Different Source Materials and Open or Closed Seed Backside

2009 ◽  
Vol 615-617 ◽  
pp. 19-22 ◽  
Author(s):  
Katarzyna Racka ◽  
Emil Tymicki ◽  
Marcin Raczkiewicz ◽  
Krzysztof Grasza ◽  
Michal Kozubal ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Single Crystals ◽  
Room Temperature ◽  
Experimental Methods ◽  
Room Temperature Resistivity ◽  
P Type ◽  
Source Materials ◽  
Type Crystal ◽  
Temperature Resistivity

n- and p-type 6H-SiC single crystals grown by PVT method using different charge materials – poly-SiC sinter or fresh SiC powder – have been studied. An open or closed seed backside during the growth processes have been applied. In the former, a distinct decrease backside etching of the seed was observed. Crystals have been extensively characterized with respect to their purity, quality and electrical properties using complex experimental methods. For the n-type boule an axially and radially homogeneous resistivity ~0.11 cm at 300 K was observed. Electrical properties of the p-type crystal, i.e., high room-temperature resistivity of 239 cm, were affected by compensation effects between residual donors (nitrogen and oxygen) and acceptors (mainly boron).

YBa2 Cu(3-x)CoxOy- A Substrate Material for YBCO Superconductors

1992 ◽  
Vol 275 ◽  
Author(s):  
J. D. Vienna ◽  
U. Balachandran ◽  
W. Cermignani ◽  
R. B. Poeppel ◽  
J. A. Taylor
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Electrical Properties ◽  
Room Temperature ◽  
Substrate Material ◽  
Nominal Composition ◽  
Room Temperature Resistivity ◽  
Cobalt Substitution ◽  
Ybco Superconductors ◽  
Temperature Resistivity

ABSTRACTThe physical properties of the ceramic YBa2Cu(3-x)CoxOy have been investigated in order to evaluate its usefulness as a substrate material for YBCO superconductors. YBa2Cu(3-x)CoxOy has been found to be thermally and chemically compatible with 123 and displays adequate electrical properties for a substrate material. A material with the nominal composition of YBa2Cu2.2CO0.8O7 was investigated, extensively. The mechanical properties of this material were found to be poor, e.g., tensile strength was only 60 MPa. A semiconductor-like behavior was observed with a room-temperature resistivity of 70 mμ.cm and a resistivity equal to 4 × 106 mn.cm at 77K. [ Key words: YBa2Cu3Oy, cobalt substitution, substrate, electrical properties, thermal properties, processing]

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.

Investigation of PTCR effect and microdefects in Nb2O5-doped BaTiO3-based ceramics by positron annihilation techniques

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744060
Author(s):  
Xuxin Cheng ◽  
Haining Cui ◽  
Xiaoxia Li ◽  
Wen Deng
Keyword(s):  
Electrical Properties ◽  
Room Temperature ◽  
Positive Temperature Coefficient ◽  
Room Temperature Resistivity ◽  
Positive Temperature ◽  
Doppler Broadening ◽  
Temperature Coefficient Of Resistance ◽  
Ptcr Effect ◽  
Temperature Resistivity ◽  
Coincidence Doppler Broadening

The influence of Nb2O5-doped concentration on the positive temperature coefficient of resistance (PTCR) effect, electrical properties and microdefects of (Ba[Formula: see text]Sr[Formula: see text])(TiNb[Formula: see text])O3 (BSTN) ceramics were investigated. Firing was conducted at 1350[Formula: see text]C for 2 h in air. The donor-doped content affected the electrical properties, PTCR effect and formation of the microdefect type of the BSTN samples. The room temperature resistivity of the BSTN specimens first decreased and then increased with increasing donor-doped content in the range of 0.2 mol.% Nb[Formula: see text] to 0.5 mol.% Nb[Formula: see text]. Moreover, the information on microdefects in BSTN ceramics was demonstrated by coincidence Doppler broadening spectrum. The influence of the defects on the PTCR characteristics of the ceramics was also revealed.

The PTCR Performance of Nb-Doped BaTiO3-NBT Ceramics

2011 ◽  
Vol 299-300 ◽  
pp. 512-515
Author(s):  
Li Zhe Li ◽  
Xing Wen Zhu ◽  
Tie Zhu Xu ◽  
Min Gong ◽  
Wen Zhong Jiang ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Curie Temperature ◽  
High Purity ◽  
Room Temperature ◽  
Second Phase ◽  
Room Temperature Resistivity ◽  
Temperature Resistance ◽  
Structural And Electrical Properties ◽  
Curie Temperature Tc ◽  
Temperature Resistivity

In this paper, Nb-doped BaTiO3-(Na0.5Bi0.5)TiO3(BBNT-Nb) based PTCR ceramic material has been prepared using high purity Nb2O5, Bi2O3, Na2CO3,TiO2and BaTiO3powders as starting materials, and its structural and electrical properties are investigated. The results indicated that the Nb2O5dopant is helpful not only to promote the formation of tetragonal BBNT structure without any second phase, but also to decrease the room-temperature resistivity. For the 0.10at% Nb-doped BBNT material with BNT content 35mol%, the properties of room-temperature resistance of 104Ω·cm, temperature coefficient (αk) of 6.3%/°C, PTCR anomaly lg(Rmax/Rmin) of 3.6 and Curie temperature (Tc) of 193°C are obtained.

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.

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