Temperature Coefficient Of Resistivity Characteristics Research Articles

Computational and Experimental Analysis of a Triode Microfuse with a WO3 Heater

In this study, high‐current‐protecting multilayered thin film microfuses are designed and simulated using the MEMS‐based tool of COMSOL multiphysics software and then fabricated and tested in the laboratory. Portable electronic devices are comprised of a secondary battery or DC charge source, and due to short circuit overcurrent, fire, and explosions can ensue. A protecting device should steadily cater to phenomena like overcurrent situations to avoid hazardous circumstances. The primary purpose of this investigation is to design a heater resistor with a negative temperature coefficient (NTC) to function as a low melting point‐based alloy for the fuse element. A lead‐tin (90Pb:10Sn wt.%) alloy has been employed as the low melting point‐based fuse element, and tungsten oxide (WO3) is integrated with the layer as a heater resistor due to its negative temperature coefficient of resistance characteristics. The electro‐thermo‐mechanical behavior is assessed, and a three‐dimensional structural modeling and simulation technique has been performed in both steady‐state and transient conditions with varying physical and electrical parameters. The heat required to melt the fuse depends on heater geometry, and when we applied 2 A current to the 1 : 30 length and width ratio‐based device, the heater achieved 600 K. Experimentally, nearly at 1 A current and above 4 V, the microfuse reached melting temperature and thus has been blown which provides a scope of controlling nearly 4 W of power electronic devices.

Comparative analysis of immittance spectroscopy of some layered structured compounds

A comparative analysis of structural and immittance characteristics of bismuth and antimony based fourfold layered perovskites BaBi4-xSbxTi4O15 (x = 1–4), synthesized by high temperature mixed oxide method are reported in this paper. The room temperature XRD data shows single phase orthorhombic crystal system for all the compounds with some variation in lattice parameters. Mostly uniformly and homogeneously distributed grains with a smaller number of voids are observed over pallet surface in SEM micrographs which exposes the good quality of the samples. Immittance spectroscopy indicates the influence of bulk and bulk boundary in the resistive and capacitive properties of the materials. The bulk resistance is found to be very small for when Bi is completely substituted by S band behaves as a good conductor. Negative temperature coefficient of resistance characteristics is observed from the impedance analysis, which confirm the semiconductor characteristics of the materials within the experimental range of temperature. Non-Debye type of relaxation mechanism is seen from the Nyquist plots. From the modulus spectroscopy, the higher capacitive properties are observed at lower temperature. The charge carriers in the samples have long-range as well as short-range ordering which are confirmed from complex impedance and modulus study of the studied samples.

Electrical characterization of CaBi4Ti3ZrO15 ceramic

Layered structured ceramic compounds have significant characteristics in the field of materials research. A new Aurivillius structured compound, CaBi4Ti3ZrO15, is processed by using solid-state reaction technique process. It is calcined at 830 °C followed by a sintering process at 880 °C. Orthorhombic structure of the material is confirmed from X-ray diffraction analysis. Grain size analysis is done through the scanning electron microscopy. Relative permittivity of the sample rises with rise in frequency and temperature and no phase transition is noticed in the experimental temperature regime. The complex impedance spectroscopy method is employed to study the immittance properties of the material within the range of frequency from 100 Hz to 10 MHz and temperature range from 30 to 500 °C. The complex impedance plot confirms the electrical behaviour of the compound which is because of the bulk and bulk interface effect. Absence of third semicircle in the complex impedance plane indicates the complete absence of electrode–materials effect on overall electrical response for this compound. The presence of non-Debye-like relaxation formalism is seen in the Nyquist plots. The temperature-dependent conductivity shows negative temperature coefficient of resistance character obeying Arrhenius equation. The temperature-dependent conductivity shows semiconducting properties of the sample. The response of hysteresis plot for the sample (P-E loop) confirms the ferroelectric property within the material.

Effect of frequency and temperature on dielectric and impedance characteristics of cerium modified BaMnO3 ceramics

In this paper, we have mainly discussed the electric field (frequency) and thermal (temperature) effect on dielectric, and electrical (impedance, electrical, and conduction) properties of a solid-state reaction technique prepared cerium modified barium manganite (BaMn0.85Ce0.15O3). The dielectric study exhibits high dielectric constant, low tangent loss, dielectric dispersion, and negative temperature coefficient of resistance characteristics which makes the material useful for energy storage devices. Preliminary analysis of the impedance and electric modulus suggests the presence of a non-Debye type of relaxation process and the role of grain and grain boundaries in the resistive and capacitive properties of the material. Both Nyquist and Cole-Cole plots confirm the semiconductor nature of the sample at high temperatures. The fitted Nyquist data with ZSIMPWIN software showed the decrease of bulk resistance from 8.841 × 107Ω (at 25 °C) to 4.085 × 103 Ω (at 500 °C) which also confirms semiconducting properties and may be found suitable applications for sensors. The analysis of ac conductivity suggests the presence of the thermally activated relaxation process in the sample.

Synthesis and electrical properties of Ba(Fe0.5Nb0.5)O3-(Na0.5Bi0.5)TiO3 ceramics

This work presents the electrical properties of (1-x)Ba(Fe0.5Nb0.5)O3-x(Na0.5Bi0.5)TiO3; 0 ≤ x ≤ 1.0 ceramics (BFN-NBT) using complex impedance spectroscopy method in a wide range of frequency (1 Hz − 1 MHz) and temperature (50 °C − 500 °C). The solid-state reaction process has been adopted to prepare these ceramics. The crystal structure and microstructure of the ceramic samples were studied. The impedance and ac conductivity studies suggested the negative temperature coefficient of resistance character as well as hopping type electrical conduction in all cases. The variation of the modulus spectrum is an intriguing temperature-dependent hopping type of mechanism for charge transport in the materials. AC conductivity data followed Jonscher’s power law, and the correlated barrier hopping explained the charge carrier transport mechanism in the system.

Temperature and Frequency Dependent Multiferroic Features of Gadolinium Doped BiFeO3-PbTiO3 Electronic System

Multiferroic gadolinium (Gd) doped BiFeO3 (BFO) and PbTiO3 (PT) samples [(Pb1−xBi0.5xGd0.5x)(FexTi1−x)O3] with x = 0.1, 0.3, 0.5 and 0.7 are formulated by adopting the solid state reaction process. The impact of gadolinium substitution in the crystal structure, morphological behavior and electrical properties has been studied. By altering the Gd concentration in the solid solution a change in the structure is observed that is from tetragonal to rhombohedral. The size of the grain in the compounds reduces as a result of enrich in gadolinium content of the furnished sample. The subsidence of lead minimizes the toxic behavior of the material with significant improvements in dielectric response of gadolinium modified BiFeO3–PbTiO3 synthesized system. From the impedance study, the material presents negative temperature coefficient of resistance characteristics and the impedance is due to the presence of grain and grain boundary effect inside the materials. It is realized that the remnant polarization decreases and frequency dependent ac conductivity increases with the concentration of gadolinium in the electronic system. From conductivity study, the equipped electronic materials show non-exponential type of conductivity relaxation.

Electrical properties of 0–3 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.2Ti0.8)O3/PVDF nanocomposites

Lead-free [Formula: see text](0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text]-([Formula: see text]PVDF ceramic–polymer nanocomposites with [Formula: see text], 0.05, 0.10, 0.15, 0.20, 0.25 were prepared using melt-mixing technique. The distribution of nanoceramic filler particles (0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text] in the PVDF matrix were examined using scanning electron microscope. Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens. Filler concentration-dependent piezoelectric coefficient ([Formula: see text] data followed exponential growth types of variation. The data for ac conductivity were found to obey Jonscher’s power law. The correlated barrier hopping (CBH) model was found to explain the mechanism of charge transport occurring in the system. The low value of loss tangent ([Formula: see text]) along with the high value of [Formula: see text] foreshadowing the prospect of present nanocomposite is a better nonlead option for piezo-sensing/detection applications, especially in bio-medical area.

Electrical and magnetic properties of 0–3 Ba(Fe1∕2Nb1∕2)O3/PVDF composites

Lead-free Ba(Fe[Formula: see text]Nb[Formula: see text]O3/PVDF 0–3 composites were fabricated using melt-mixing technique. X-ray diffraction, scanning electron microscopy, dielectric, impedance, ac conductivity, magnetic force microscopy (MFM) and vibrating sample magnetometer studies were undertaken to characterize the samples. Average crystallite size of the Ba(Fe[Formula: see text]Nb[Formula: see text]O3 powder, estimated using Williamson–Hall approach, was found to be [Formula: see text][Formula: see text]nm. The filler particles of [Formula: see text][Formula: see text][Formula: see text]m were found to disperse in the polymer matrix of all the composites. Filler concentration-dependent values of real and imaginary parts of complex permittivity showed increasing trend and were seen to follow Bruggeman and Furukawa equations. The data for ac conductivity exhibited negative temperature coefficient of resistance character of the test materials and were found to obey Jonscher’s power law. The correlated barrier hopping model was found to explain satisfactorily the mechanism of charge transport occurring in the system. MFM confirmed the presence of magnetic phases in the composites. Typical magnetization versus applied field curves indicated the possibility of magnetoelectric coupling in the system. Hence, the present composites have shown themselves as potential multi-functional candidate materials for use in high density data storage applications.

Investigation on microdefects and positive temperature coefficient of resistivity characteristics in donor-doped BaTiO3-based ceramics by using positron annihilation techniques

Positron annihilation techniques were used to study the effects of Nb dopant content and cooling modes on the electrical properties and positive temperature coefficient of resistivity (PTCR) characteristics of (Ba0.95Sr0.05) (TiNbx)O3 (BSTN) ceramics sintered at 1350°C for 2h in air. Cooling methods and dopant concentration influence the PTCR effect, electrical properties and type of microdefect formation in BSTN specimens. The highest peak is observed in BSTN ceramics cooled at 1200°C for 2h after sintering at 1350°C for 2h in air. The 3d electrons of the defect vacancies are easily annihilated by the positron. The main peak of the ratio curves is located at about 11.84×10–3m0c for the samples air cooled at 1200°C for 2h after sintering at 1350°C for 2h in air. This peak is positioned lower at approximately 10.85×10–3m0c for the specimens obtained by furnace cooling and cooling at 1100°C for 2h. The low room-temperature resistance of BSTN ceramics can be achieved through furnace cooling, whereas the high resistance jump can be obtained by sintering at 1200°C for 2h during cooling.

Electrical Properties of a Lead-Free Perovskite Ceramic: Ba(Gd1/2Nb1/2)O3

Polycrystalline Ba(Gd1/2Nb1/2)O3 was prepared using a hightemperature solid-state reaction method. X-ray diffraction analysis indicated the formation of a single-phase cubic structure having space group m Pm3 . AC impedance plots as a function of frequency at different temperatures were used to analyse the electrical behaviour of the sample, which indicated the negative temperature coefficient of resistance character. Complex impedance analysis targeted non-Debye type dielectric relaxation. Frequency dependent ac conductivity data obeyed Jonscher’s power law. The apparent activation energy was estimated to be 0.17 eV at 1

Impedance and a.c. conductivity studies of Ba(Pr1/2Nb1/2)O3 ceramic

Impedance and electrical conduction studies of Ba(Pr1/2Nb1/2)O3 ceramic prepared through conventional ceramic fabrication technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group, \({Pm\overline 3 m}\). EDAX and SEM studies were carried out to study the quality and purity of compound. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using impedance data. Complex impedance as well as electric modulus analyses suggested dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Pr1/2Nb1/2)O3. The a.c. conductivity data were used to evaluate density of states at Fermi level, minimum hopping length and apparent activation energy.

Study of structural, magnetic and electrical properties on Ho-substituted BiFeO3

The polycrystalline Bi1−xHoxFeO3 (x=0, 0.05, 0.1) compounds were synthesized by conventional solid-state route. Rietveld refinement revealed that all the compounds were stabilized in rhombohedral structure with R3c (IUCr No. 161) space group. Room temperature magnetic measurements revealed that Ho substitution induces ferromagnetism and improves the magnetic properties of BiFeO3. A competing ferro and anti-ferro magnetic interaction was observed in these compounds. Temperature variation of complex impedance studies revealed that electrical properties are improved with the Ho substitution. The ac conductivity found to obey universal power law and showed the negative temperature coefficient of resistance character. Correlated barrier hopping model (CBH) was employed to explain the frequency and temperature dependence of ac conductivity and the mechanism of transport in the material BFO and Ho substituted BFO. Density of states near Fermi level was calculated by using the ac conductivity data.

PTCR characteristics of polycarbonate/nickel‐coated graphite‐based conducting polymeric composites in presence of poly(caprolactone)

AbstractThe effect of poly(caprolactone) (PCL) on the positive temperature coefficient of resistivity characteristics of polycarbonate (PC)/nickel (Ni)‐coated graphite (40 wt%) composites was investigated. The PTC trip temperature of PC/Ni‐coated graphite composites appeared at 155°C. On addition of PCL to PC/Ni‐coated graphite composites, the PTC trip temperature reduced to 125°C, well below the Tg of the PC (∼147°C), as well as the PC/PCL (∼136°C) blend. It is noteworthy that the observed PTC effect for PC/PCL (8 wt%)/Ni‐coated graphite (40 wt%) composites is highly reproducible during many heating cycles. The coefficient of thermal expansion (CTE) of PC was increased in presence of PCL. Thus, the mismatch in CTE of the PC and Ni‐coated graphite at a temperature well below the Tg of PC was enough to disrupt the continuous network structure that increased the resistivity of the composites. Storage modulus of PC/PCL/Ni‐coated graphite composites was higher than PC/Ni‐coated graphite composites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Microstructure and Positive Temperature Coefficient of Resistivity Characteristics of Na2Ti6O13-Doped 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 Ceramics

The microstructure and positive temperature coefficient of resistivity (PTCR) characteristics of 0.1 mol% doped (BBNT-NT001) ceramics sintered at various temperatures from to were investigated in order to develop eco-friendly PTCR thermistors with a high Curie temperature (). Resulting thermistors showed a perovskite structure with a tetragonal symmetry. When sintered at , the specimen had a uniform microstructure with small grains. However, abnormally grown grains started to appear at and a homogeneous microstructure with large grains was exhibited when the sintering temperature reached . When the temperature exceeded , the grain growth was inhibited due to the numerous nucleation sites generated at the extremely high temperature. It is considered that is responsible for the grain growth of the ) ceramics by forming a liquid phase during the sintering at around . The grain growth of the BBNT-NT001 ceramics was significantly correlated with a decrease of resistivity. All the specimens were observed to have PTCR characteristics except for the sample sintered at . The BBNT-NT001 ceramics had significantly decreased and increased resistivity jump with increasing sintering temperature at from to . Especially, the BBNT-NT001 ceramics sintered at exhibited superior PTCR characteristics of low resistivity at room temperature (), high resistivity jump (), high resistivity temperature factor (20.4%/), and a high Tc of .

Impedance spectroscopy of Ba3Sr2DyTi3V7O30 ceramic

Polycrystalline sample of Ba3Sr2DyTi3V7O30 was prepared at 950°C using a high-temperature solid-state reaction technique. X-ray structural analysis indicated the formation of a single-phase orthorhombic structure with lattice parameters: a = 12·2719 (39) Å, b = 8·9715(39) Å and c = 19·7812(39) Å. Microstructural study showed densely packed uniform distribution of grains over the surface of the sample. The a.c. impedance plots were used as tools to analyse the electrical response of the sample as a function of frequency at different temperatures (30–500°C). These plots revealed the presence of grain boundary effect, from 200·C onwards. Complex impedance analysis showed non-Debye type of dielectric relaxation. The Nyquist plots showed the negative temperature coefficient of resistance character of Ba3Sr2DyTi3V7O30. A hopping mechanism of electrical transport processes in the system is evident from the modulus analysis. The activation energy of the compound (calculated both from loss and modulus spectrum) is the same, and hence the relaxation process may be attributed to the same type of charge carrier.

Electrical conduction in (Na0·5Bi0·5)TiO3 ceramic: impedance spectroscopy analysis

Polycrystalline sample of (Na0·5Bi0·5)TiO3 was prepared using a high temperature solid-state reaction synthesis at 1070°C and subsequent sintering at 1100°C in oxygen atmosphere. X-ray diffraction (XRD) analysis of (Na0·5Bi0·5)TiO3 powder indicated the formation of a single phase rhombohedral structure. Dielectric study revealed the diffuse phase transition at 340°C. The ac conductivity data were found to obey power law and showed negative temperature coefficient of resistance character. Complex electric modulus analysis indicated non-Debye type dielectric relaxation in the system. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and activation energy of the compound. The correlated barrier hopping model was found to successfully explain the mechanism of charge transport in (Na0·5Bi0·5)TiO3.

Influence of Ba/Ti Ratio on the Positive Temperature Coefficient of Resistivity Characteristics of Ca‐Doped Semiconducting BaTiO3 Fired in Reducing Atmosphere and Reoxidized in Air

The positive temperature coefficient of resistivity (PTCR) characteristics of donor‐doped BaTiO3 fired in a reducing atmosphere and reoxidized in air are investigated. The result reveals that conventional semiconducting BaTiO3 ceramics fired in a reducing atmosphere and reoxidized at a low temperature of 800°C in air show minimal PTCR characteristics, as reported earlier; however, Ca‐doped BaTiO3 with compositions in the range of 1.005≤(Ba+Ca+La)/Ti≤1.010 exhibit pronounced PTCR characteristics, even when reoxidized at such a low temperature. The semiconducting BaTiO3 ceramics with {(Ba+Ca+La)/Ti}=1.005 and Ca‐doped to 20 mol% exhibit remarkable PTCR characteristics with a resistivity jump of two orders of magnitude when they have been reoxidized at 800°C after firing in a reducing atmosphere.

Effects of Ba/Ti Ratio on Positive Temperature Coefficient of Resistivity Characteristics of Donor-doped BaTiO3 Fired in Reducing Atmosphere

The positive temperature coefficient (PTC) of resistivity characteristics of donor-doped BaTiO3 fired at 1350 °C in a reducing atmosphere of 1×10-7 MPa at the partial pressure of oxygen is investigated. The result reveals that BaTiO3 ceramics fired in such a reducing atmosphere usually exhibit low PTC characteristics, whereas La-doped BaTiO3 with compositions in the range of (Ba+La)/Ti≧1.02 exhibit pronounced PTC characteristics. A La content of less than 0.4 mol % is suitable for the PTC characteristics, while samples doped with more than 0.8 mol % La do not show the PTC characteristics. The PTC characteristics of semiconducting BaTiO3 fired in a reducing atmosphere are enhanced with a decrease in the ion radius of a donor ion in the order La<Nd<Sm, therefore, semiconducting BaTiO3 doped with Sm shows pronounced PTC characteristics with a resistivity increase of more than 6 orders of magnitude. However, the resistivity of BaTiO3 ceramics doped with Y, whose ion radius is less than that of Sm, is extremely high resistivity that decreases with increasing temperature, thereby indicating only a negative temperature coefficient (NTC) characteristics.

Structure, synthesis and high dielectric property of (NaBi)(NbCr)O 6 pyrochlores

Pyrochlores with composition (NaBi)(NbCr)O 6 were sintered in the temperature range of 1100–1250 °C. Dielectric properties of the ceramics were investigated in a wide range of temperatures of − 15 to 200 °C and frequencies of 1–800 kHz. The suitable sintering temperatures for (NaBi)(NbCr)O 6 ceramics are suggested from 1150 to 1200 °C. The dielectric constant behavior reflects, in our opinion, the formation of the space charge and the orientational polarization. The pyrochlores have convex resistivity-temperature characteristics around the transition point, and exhibit the negative temperature coefficient of resistance characteristics. The activation energies of conductivity of samples were obtained at various sintering temperatures.

Sintering condition and PTCR characteristics of porous (Ba,Sr)(Ti,Sb)O3

We fabricated porous (Ba,Sr)(Ti,Sb)O3 ceramics by adding potato-starch (1–20 wt %) and investigated the effects of sintering temperature (1300–1450 °C) and time (0.5–10 h) on the positive temperature coefficient of resistivity characteristics of the porous ceramics. The room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O3 ceramics decreased with increasing sintering temperature, while that of the ceramics increased with increasing sintering time. For example, the room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O3 ceramics for the samples sintered at 1300 °C and 1450 °C for 1 h is 6.8×103 and 5.7×102 Ω cm, respectively, while that of the ceramics is 6.5×102 and 1.3×107 Ω cm, respectively, for the samples sintered at 1350 °C for 0.5 h and 10 h. In order to investigate the reason for the decrease and increase of room-temperature electrical resistivity of the samples with increasing sintering temperature and time, the average grain size, porosity, donor concentration of grains (Nd), and electrical barrier height of grain boundaries (Φ) of the samples are discussed.