Composite ceramics with a positive temperature coefficient of electrical resistivity effect

2000 ◽  
Vol 15 (2) ◽  
pp. 417-428 ◽  
Author(s):  
Darja Lisjak ◽  
Miha Drofenik ◽  
Drago Kolar
Keyword(s):  
Electrical Resistivity ◽  
Thermal Expansion ◽  
Temperature Coefficient ◽  
Linear Thermal Expansion ◽  
Positive Temperature Coefficient ◽  
High Resistivity ◽  
Positive Temperature ◽  
Composite Ceramics ◽  
Ptcr Effect ◽  
Constituent Phase

Composite ceramics with compositions within the ZnO–NiO–TiO2, ZnO–MgO, and ZnO–Ln2O3 (Ln = Nd, Sm) systems were found to exhibit an anomalous positive temperature coefficient of electrical resistivity (PTCR) effect. The investigations revealed, that in all cases when the PTCR effect was identified, the composite ceramics were found to be composed of phases with different electrical resistivities and linear thermal expansion coefficients. Thermal mismatch between the phases in the composites leads to a disconnection of the grains of the low resistivity constituent phase on account of the high thermal expansion of the other high resistivity constituent phase, resulting in a PTCR effect.

Positive temperature coefficient of resistivity effect in Pb-doped KnbO3

2002 ◽  
Vol 17 (12) ◽  
pp. 2989-2992 ◽  
Author(s):  
Irena Pribošič ◽  
Darko Makovec ◽  
Miha Drofenik
Keyword(s):  
Phase Transition ◽  
Temperature Coefficient ◽  
Ferroelectric Material ◽  
Positive Temperature Coefficient ◽  
Cubic Phase ◽  
Room Temperature Resistivity ◽  
Positive Temperature ◽  
Ptcr Effect ◽  
Temperature Coefficient Of Resistivity ◽  
Temperature Resistivity

KnbO3 is a ferroelectric material with a Curie temperature (TC) at 415°C, thus giving it the potential to be a material for high-temperature positive temperature coefficient of resistivity (PTCR) applications. In this study, we investigated the PTCR effect in donor-doped KnbO3 ceramics containing 0, 0.1, 0.2, and 0.3 mol% PbO. The donor-doped KnbO3 ceramics exhibited a PTCR anomaly with a relatively low room-temperature resistivity. The temperature of the tetragonal-to-cubic phase transition (TC) of the KnbO3 decreased with the amount of added PbO, while the orthorhombic-to-tetragonal phase transition (TOT) remained unchanged.

Positive temperature coefficient resistance effect in Ba1-xSrxTiO3 ceramics modified with Bi2O3 and PbO by a vapor-doping method

1999 ◽  
Vol 14 (8) ◽  
pp. 3328-3329 ◽  
Author(s):  
Jianquan Qi ◽  
Zhilun Gui ◽  
Longtu Li ◽  
Yajing Wu
Keyword(s):  
Temperature Coefficient ◽  
Defect Chemistry ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Ptcr Effect ◽  
Pb Doping

Ba1−xSrxTiO3-based positive temperature coefficient resistance (PTCR) ceramics were prepared by use of a vapor-doping method. When doped with Bi, the PTCR effect is improved; when doped with lead, however, the effect is weakened. The different influences of Bi and Pb doping on the ceramic properties are discussed in terms of the defect chemistry.

Influence of the Metal Particle Size and Sintering Process on the Electrical Resistivity of m-ZrO2/30%Mo Cermet

2015 ◽  
Vol 816 ◽  
pp. 205-209 ◽  
Author(s):  
Yan Ling Guo ◽  
Hai Zhao ◽  
Lei Tang ◽  
Yao Jie Wang ◽  
Jie Yu Zhang
Keyword(s):  
Electrical Conductivity ◽  
Particle Size ◽  
Electrical Resistivity ◽  
Metal Particle ◽  
Positive Temperature Coefficient ◽  
High Resistivity ◽  
Average Particle ◽  
Positive Temperature ◽  
Sintering Process ◽  
Metal Particle Size

Monolithic zirconia-molybdenum (m-ZrO2/Mo) cermets have been prepared by traditional powder metallurgy process with molybdenum volume concentration of 30% and different molybdenum powders with average particle sizes of 80nm, 3μm, 8μm and 13μm. The influence of metal particle size on the morphology and electrical conductivity of the cermet has been investigated. The electrical resistivity of the cermet was measured via 4-probe DC technique from 500 °C to 1600 °C. All the samples showed the positive temperature coefficient of electrical resistivity, but the sample prepared with 80 nm molybdenum powder showed very high resistivity over 0.5 Ω·cm. Hot-press sintering was proved to be helpful to the elongated conductive phase formation, thus the electrical conductivity of cermet increased compared to the pressureless sintering process.

Positive Temperature Coefficient of Electrical Resistivity below 150 K in Barium Strontium Titanate

2004 ◽  
Vol 87 (4) ◽  
pp. 756-758 ◽  
Author(s):  
Massimo Viviani ◽  
Marcello Leoni ◽  
Maria Teresa Buscaglia ◽  
Vincenzo Buscaglia ◽  
Paolo Nanni
Keyword(s):  
Electrical Resistivity ◽  
Temperature Coefficient ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Barium Strontium

Positive Temperature Coefficient of Resistance in MOCVD (Ba0.75Sr0.25)Ti1+yO3+z Films

2002 ◽  
Vol 748 ◽  
Author(s):  
S. Saha ◽  
D. Y. Kaufman ◽  
S. K. Streiffer ◽  
R. A. Erck ◽  
O. Auciello
Keyword(s):  
Temperature Coefficient ◽  
Weak Field ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Temperature Coefficient Of Resistance ◽  
Current Voltage ◽  
Ptcr Effect ◽  
Bst Films ◽  
Current Voltage Characteristics ◽  
Increasing Temperature

ABSTRACTThe leakage and dielectric properties of a thickness series (90–480 nm) of {100} fiber-textured MOCVD (Ba0.75Sr0.25)Ti1+yO3+z (BST) thin films on Pt/SiO2/Si were investigated. The temperature and voltage dependence of the permittivity were consistent with previous observations, where thinner films demonstrated a suppressed temperature and electric field response that transitioned to a more bulk-like response with increasing film thickness. The current-voltage characteristics showed two distinct regimes. At low fields the current displayed weak field dependence and a monotonic increase with increasing temperature. In contrast, positive temperature coefficient of resistance (PTCR) was observed in the high-field leakage current behavior. The PTCR behavior was more pronounced for thicker BST films. Factors contributing to the observed PTCR effect are outlined and contrasted with the description for bulk BaTiO3 ceramics.

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