High Temperature Electrical Properties Research Articles

Effect of striae on the high temperature dielectric and electrical properties of lithium aluminosilicate glass-ceramics

Lithium Aluminosilicate glass-ceramics with striae (LAS-WS) and without striae (LAS-WoS) were processed using melt casting technique. LAS-WS and LAS-WoS samples were characterized and found stress birefringence >10 nm/cm and <10 nm/cm, respectively. LAS-WS and LAS-WoS samples were subjected to structural, microstructural, high temperature dielectric and electrical characterization. The presence of striation did not significantly affected the formation of β-spondumene structure during crystallization heat treatment. TEM image confirms the formation of nanocrystals in the glass matrix of lithium aluminosilicate glass-ceramics. The homogeneous distribution of LAS nanocrystals of average size of 3–6 nm is evident from TEM results. Stress birefringence distribution in lithium aluminosilicate glass-ceramic clearly shows the striae formation. Shadowgraphy images confirmed the striae free and striae containing regions in the glass-ceramic. The effect of striae on dielectric properties and AC conductivity was analysed using impedance spectroscopy and it was found that the value of the relative permittivity decreased from 415 (1.2 Hz) to 9.76 (1.2 MHz) for LAS-WoS and from 401 (1.2 Hz) to 10.3 (1.2 MHz) for LAS-WS, respectively. It was found that striae in LAS glass-ceramics influence the electrical impedance and AC conductivity relaxation process rather than relative permittivity. The effect of striae on crystallization and morphology are presented. Both the samples have shown crystallinity of more than 75 %. The electrical conductivity of σ = 2.0 × 10−3 S/cm for LAS-WoS and 2.7 × 10−3 S/cm for LAS-WS at 300 °C as well as σ = 4.6 × 10−3 S/cm for LAS-WoS and 6.9 × 10−3 S/cm for LAS-WS at 700 °C are found to be in good agreement due to increase in the electrical conductivity with temperature. The ionic conductivity of the material due to Li-ion mobility with respect to temperature and electric field and possible mechanism of AC conductivity are discussed. The results presented indicates the potential application of this material that demands high temperature operation of lithium aluminosilicate glass-ceramics.

Comparative Study on High-Temperature Electrical Properties of 1.2 kV SiC MOSFET and JBS-Integrated MOSFET

Comparative Study on High-Temperature Electrical Properties of 1.2 kV SiC MOSFET and JBS-Integrated MOSFET

Optical, electrical, and crystal structure study of BaZr0.01Ti0.99O3 ceramics modified with Gd3+ and Y3+ rare-earth ions

Ceramics with compositions Ba0.95Gd0.034Ti0.99Zr0.01O3 (BGdZT) and Ba0.95Y0.034Ti0.99Zr0.01O3 (BYZT) were prepared using the solid-state reaction method. The single tetragonal phase (space group P4mm) of BGdZT and BYZT ceramics is verified by analyzing X-ray spectra using the Rietveld method. The analysis of the tolerance factor (t) reveals an order-disorder phase transition in the tetragonal structure, resulting from the displacement of Ti4+/Zr4+ along the c-axis. A significant correlation is observed between the tolerance factor (t) and the phase transition temperature (Tc), as well as between the band gap of optical measurements and the degree of displacement of Ti4+/Zr4+ along the c-axis. The analysis of high-temperature electrical properties indicates that the conduction mechanism in both studied materials is a correlated barrier hopping (CBH) model, and electrical conductivity improves with increasing densification. The non-Debye behavior is confirmed by the curves of the M′′ vs.ƒ(Hz). The combination of M′′/M′′max and Z′′/Z′′max traces confirms the type of short-range charge carrier mobility.

High-Temperature Reliability of Nano-Ag Sintered Joints on Ag-Plated Cu Substrates

As an emerging lead-free packaging interconnect material, Nano-Ag paste exhibits superior high-temperature mechanical, electrical, and thermal properties. It can meet the stringent high-temperature and high-density packaging requirements of future high-power semiconductor devices and is garnering widespread attention. However, research on the high-temperature reliability of sintered joints remains rather limited. In this study, we fabricated high-strength hot-press sintered nano-Ag joints using a hot-press sintering process. These joints underwent aging at high temperatures of 200°C and 300°C, yielding insights into the variations in mechanical properties at different temperatures. The reasons behind joint failure were analyzed by investigating the evolution of joint microstructures and fracture surfaces. The results indicate that even after extended aging at 200°C, the joint strength can still be maintained at 176 MPa. However, after aging for over 100 hours at 300°C, the joint fails. The growth of Cu oxides was observed within the joint microstructure, which constitutes the primary cause of joint failure at 300°C.

Application of the van der Pauw method for electrical conductivity measurements at high temperatures using an insulating compressing ring.

High quality data on the high temperature electrical properties of ceramics, particularly oxides, is of great value for material selection, design, and modeling for a broad range of emerging applications. Utilizing the mismatch in the coefficient of thermal expansion between two materials, a purely mechanical method for establishing electrical contact in the van der Pauw geometry to measure the bulk resistivity of ceramic disks at high temperatures is presented. Measurements of a reference material, 20 mol. % Gd-doped cerium oxide, are presented up to 1000 °C. The viability of electrical measurements up to a maximum temperature of 1600 °C is also considered. Measurements are performed using multiple techniques and compared to literature values finding excellent agreement. The approach described in this work enables the van der Pauw method to be applied to many ceramic materials over a wide range of temperatures and environments.

Defect-engineered graphene-on-silicon-carbide platform for magnetic field sensing at greatly elevated temperatures

High-temperature electrical properties of p-type hydrogen-intercalated quasi-free-standing epitaxial Chemical Vapor Deposition graphene on semi-insulating vanadium-compensated on-axis 6H-SiC(0001) and high-purity on-axis 4H-SiC(0001) originate from the double-carrier system of spontaneous-polarization-induced holes in graphene and thermally-activated electrons in the substrate. In this study, we pre-epitaxially modify SiC by implanting hydrogen (H+) and helium (He+) ions with energies ranging from 20 keV to 50 keV to reconstruct its post-epitaxial defect structure and suppress the thermally-developed electron channel. Through a combination of dark current measurements and High-Resolution Photo-Induced Transient Spectroscopy between 300 K and 700 K, we monitor the impact of ion bombardment on the transport properties of SiC and reveal activation energies of the individual deep-level defects. We find that the ion implantation has a negligible effect on 6H-SiC. Yet in 4H-SiC, it shifts the Fermi level from ∼600 meV to ∼800 meV below the minimum of the conduction band and reduces the electron concentration by two orders of magnitude. Specifically, it eliminates deep electron traps related to silicon vacancies in the charge state (2-/-) occupying the h and k sites of the 4H-SiC lattice. Finally, we directly implement the protocol of deep-level defect engineering in the technology of amorphous-aluminum-oxide-passivated Hall effect sensors and introduce a mature sensory platform with record-linear current-mode sensitivity of approximately 80 V/AT with -0.03-%/K stability in a broad temperature range between 300 K and 770 K, and likely far beyond 770 K.

High-temperature electrical and optical properties of sputtered iridium at wavelengths of 300 nm to 15 µm

Due to its refractory properties and higher oxidation resistance, iridium (Ir) exhibits great potential for applications such as thermophotovoltaic emitters or contamination sensing. However, the lack of its temperature-dependent optical data prevents accurate modeling of Ir-based optical devices operating at higher temperatures. In this work, refractive indices of as-deposited and annealed Ir films, sputter-deposited, are characterized at between room temperature and 550°C over 300 nm to 15 µm of wavelength. The extinction coefficients of both as-deposited and annealed Ir films tend to decrease as temperature increases, with the exception of as-deposited Ir at 550°C due to significant grain growth. Under 530°C, optical constants of as-deposited Ir are less sensitive to temperature than those of annealed Ir. These characteristics of Ir films are correlated with their microstructural changes.

Modification of high-temperature electrical properties in CaTiO3 ceramics by Sm3+ and Al3+ doping

Modification of high-temperature electrical properties in CaTiO3 ceramics by Sm3+ and Al3+ doping

Enabling High-Performance Polypropylene Nanocomposites With Interfacial Deep Traps

Polymer nanocomposites are the material of choice for dc insulation. The emerging demand for high-capacity high voltage direct current (HVdc) power transmission requires polymer nanocomposites capable of safe and stable operation at high temperatures. However, the high-temperature electrical properties of current polymer nanocomposites are still unsatisfactory. Here, we report that the modulation of polymer/nanoparticle interfaces can greatly improve the high-temperature insulation properties of polypropylene (PP)-based nanocomposite for recyclable HVdc cable insulation application. The nanoparticles are surface-modified with PP-graft-maleic anhydride (PP- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${g}$ </tex-math></inline-formula> -mah), which is not only well miscible with PP but also contains polar groups to act as interfacial deep traps. We demonstrate that the interfacial deep traps can improve the dc breakdown strength and the electrical resistivity of polymer nanocomposite by inhibiting the charge injection. This work deepens the understanding of interfacial effects in polymer nanocomposites and provides new opportunities for designing high-performance recyclable insulation materials for HVdc cables.

Improved High-Temperature Electrical Properties of Polymeric Material by Grafting Modification

Improved High-Temperature Electrical Properties of Polymeric Material by Grafting Modification

High-temperature characteristics and electrical properties of CrN-coated and Mn/Cu/CrN-coated 430 stainless steel for solid oxide fuel cell metal interconnects

High-temperature characteristics and electrical properties of CrN-coated and Mn/Cu/CrN-coated 430 stainless steel for solid oxide fuel cell metal interconnects

High-entropy (Ca0.5Ce0.5)(Nb0.25Ta0.25Mo0.25W0.25)O4 scheelite ceramics with high-temperature negative temperature coefficient (NTC) property for thermistor materials

(Ca0.5Ce0.5)(Nb0.25Ta0.25Mo0.25W0.25)O4 high-entropy ceramics with single scheelite phase structure were synthesized by solid-state reactions under a reducing atmosphere of argon, and their high-temperature electrical properties were investigated. The single scheelite phase of high-entropy ceramics is fabricated at a sintering temperature of 1300 °C, and grain sizes as well as relative densities of high-entropy ceramics increase with the increase of sintering temperature. High-entropy ceramics sintered at 1300 °C and 1400 °C exhibit excellent negative temperature coefficient (NTC) property within an ultrawide temperature range of 150 °C-1200 °C. Ceramic samples sintered under Ar tend to have lower activation energy, for the higher Ce3+ contents they possess than those sintered under air are in favor of increasing their polaron concentration. In comparison with conventional scheelite ceramics, high-entropy scheelite ceramics have a unitary NTC mechanism within a wider temperature range and a better aging property, for their crystal structure is stabilized by high-entropy effect at higher temperature.

High-temperature electrical properties of polymer-derived ceramic SiBCN thin films fabricated by direct writing

The in situ temperature monitoring of hot components in harsh environments remains a challenging task. In this study, SiBCN thin-film resistance grids with thicknesses of 1.8 μm were fabricated on alumina substrates via direct writing. Owing to their dense microscopic morphology and extremely high graphitisation level, the produced SiBCN films exhibited large high-temperature oxidation resistance and electrical conductivity. The resistance–temperature, stability, and repeatability characteristics of these films were examined in an aerobic environment at temperatures up to 800 °C. The obtained results revealed that the thermistor resistance decreased monotonously with increasing temperature from room temperature to 800 °C. The SiBCN film resistance variations observed during repeated temperature cycling in the regions of 505–620 °C and 610–720 °C were 0.09% and 1.7%, respectively. The high cyclability and stability of the SiBCN thin film thermistor suggested its potential applicability for the in situ temperature monitoring of hot components in harsh environments.

Microstructure and Electrical Properties of Lanthanides-doped CaBi2Nb2O9 Ceramics

Calcium bismuth niobate (CaBi2Nb2O9, CBN) is a promising candidate for high-temperature applications in aerospace, shipping, and nuclear industries, owing to its ultra-high Curie temperature (TC∼x223C 940 °C). Lanthanide ions modified CBN based ceramics were prepared by a conventional solid-state sintering route. The crystal structure, microstructure, and high-temperature electrical properties of CBN ceramics doped by different lanthanide dopants (La, Ce, Nd, Sm, Dy, Er, Yb) were studied and the underlying mechanism was also discussed. Among these doping ions, Ce3+/Ce4+ doping CBN ceramics exhibits anomalous electrical properties. Impedance analysis was introduced to clarify the difference in electrical properties of lanthanide-doped CBN ceramics at high temperatures. As a result, the anomalous electrical properties are attributed to the extrinsic oxygen vacancies induced by the Ce doping. These results could assist to tailor the electrical properties of Aurivillius phase ceramics with lanthanide modifications.

High Temperature Electrical Properties of Co-Substituted La4BaCu5O13+δ Thin Films Fabricated by Sputtering Method.

The high-temperature conductivity of the perovskite oxides of a La4BaCu5O13+δ (LBCO) thin film prepared by RF sputtering deposition and thermal annealing has been studied. While the bulk LBCO compound was metallic, the LBCO film deposited on a Si substrate by sputtering and a post annealing process showed semiconductor-like conduction, which is considered to be due to the defects and poor grain connectivity in the LBCO film on the Si substrate. The LBCO film deposited on a SrTiO3 substrate was of high film quality and showed metallic conduction. When the cation site Cu was substituted by Co, the electrical conductivity of the LBCO film increased further and its temperature dependence became smaller. The transport properties of LBCO films are investigated to understand its carrier generation mechanism.

Investigations on structural, optical, high temperature electrical and ferroelectric properties of Neodymium doped rubidium titanyl phosphate single crystal

Neodymium doped Rubidium Titanyl Phosphate (RTP) single crystal was grown using a high-temperature flux solution method with rubidium polyphosphate flux. Though doping does not induce changes in growth temperature, variations in material properties were observed while characterizing the grown crystal. Powder x-ray diffraction and high resolution x-ray diffraction analysis of Nd: RTP single crystal suggested the orthorhombic structure with small structural distortion and good crystalline nature. The presence of neodymium and other elements in the crystal was confirmed using EDAX analysis. The optical quality of the material was studied using optical transmittance and absorption studies. The variation in the optical band gap due to Nd doping was also analyzed. The dielectric polarization, ion hopping, activation processes, dielectric, electrical conductivity, and resistivity nature of the grown crystal were studied using impedance analysis. The properties were studied from room temperature to 850 °C, in the frequencies range from 100 Hz to 8 MHz. Then the results were compared with flux-grown pure RTP single crystals. The result exhibited superior properties on Nd doping in RTP. The low and static dielectric constant exhibited by Nd: RTP made it suitable for NLO applications. The ferroelectric nature of the Nd: RTP was analyzed from room temperature to 180 °C at an applied field of 4 kV and the PE loop was found with values of polarization and coercive field as 0.15 μC/cm2 and 1.79 kV/cm, respectively. Nd: RTP does not show any polarization decay up to 5000 frequency cycles confirmed by fatigue analysis.

Evidence of Weak Ferromagnetism, Space Charge Polarization, and Metal to Insulator Transition in Dy-Doped CaMnO3

The effect of Dy doping on CaMnO3 (CDMO) has been thoroughly investigated. The room-temperature structure, low-temperature magnetic transitions, and high-temperature electrical properties of CDMO were studied using X-ray diffraction, magnetization, and dielectric techniques. The CDMO exhibits an orthorhombic structure with Pnma symmetry. The low-temperature magnetic susceptibility data show the ferromagnetic domains embedded in the antiferromagnetic structure (G-type), and it confirms the Neel temperature (TN) approximately 55 K. Temperature-dependent dielectric data measured using a few selected frequencies show a high dielectric constant ~ 29,108,808 at 1 kHz. The presence of a high dielectric constant at the lower frequency side can be attributed to the space charge polarization (SCP) and compositional disorder (heterogeneity) in the compounds. The impedance cole-cole plot shows a depressed semicircle; mathematically these data were fitted by the Kohlrausch-Williams-Watt model. From this model obtained two mechanisms: (i) the electric modulus divulges the CDMO ceramic tails the Non-Debye type of relaxation and (ii) the electric modulus peak shifting evidence the charge carrier mobility from long range to short range. High-temperature dielectric, resistivity, and conductivity data show a clear anomaly around 461 K, owing to metal to insulator transition.

Effect of titanium carbide powder as a filler on the mechanical properties of silicone rubber

Silicone rubber is the most commonly used polymer. The properties include high and low temperature stability, inertness, odourless, high elasticity, durability, electrical properties and transparency. Silicone rubber is composed of silicone polymer and molecules like carbon, hydrogen and oxygen. Recent times, some drawbacks like hardness, have emerged and there have been extensive efforts in research to improve its properties. This work is intended to study the effect of Titanium Carbide in particle form on the mechanical properties of Silicone Rubber. The amount of Titanium Carbide is 0, 1, 2 and 5 parts by weight per hundred parts of rubber [phr] taken in 4 samples. An experimental study has been conducted on all the samples to determine the mechanical properties of all the samples. The obtained results indicate the cure time increases at 1% TiC and reduces gradually, specific gravity increases constantly, tensile strength has maximum value at 1% TiC, tear strength shows its peak at 2% TiC, hardness of the samples increases gradually as the percentage of Titanium Carbide increases, elongation percentage has a peak value for 1% TiC sample.

Relaxation dynamics associated with the multiple polymorphic phase transitions in morphotropic phase boundaries BiScO3-PbTiO3 solid solutions

High temperature electrical properties of morphotropic phase boundary BiScO3-PbTiO3 compositions, exhibiting high piezoelectric coefficient, saturation polarization, field induced strain and low dielectric loss have been presented in detail. Dielectric loss and various electrical parameters have been comprehensively utilized to identify multiple dipolar relaxation dynamics in the regime where conductivity effects are low. Dielectric data confirms presence of various polymorphs exhibiting lower (higher) symmetry configuration, which extends to wider (narrower) temperature regime. Effect of conductivity associated with the charge transport is not dominant up to 600 K, which shows that this material is a promising candidate for high temperature applications.

Heat capacity and high temperature electrical transport properties of TbNiC2

The single phase polycrystalline TbNiC2 sample was obtained by annealing at 1073 K. The compound adopts structure of CeNiC2-type, confirmed by XRD Rietveld refinement: space group Amm2, a = 3.6000(2) Å, b = 4.5129(2) Å, c = 6.0563(3), RB(I) = 3.72%, Rp = 5.46%. The orthorhombic CeNiC2 crystal structure prototype is shown to be derived from the hexagonal AlB2 one (space group P6/mmm) following the Bärnighausen formalism via translationengleiche. Zero-field heat capacity measurements of TbNiC2 in the range of 1.9–300 K reveal Sommerfeld coefficient γ = 8(1) mJ mol−1 K−2, phonon coefficient β = 1.18(1)∙10−4 J mol−1 K−4 with the derived Debye temperature of ΘD ≈ 404 K and antiferromagnetic state below TN = 25 K with a spin-wave excitation gap of Δ = 26(2) K. The 4f-electron contribution to the magnetic entropy change indicates a doublet ground state for a non-Kramer's Tb3+ ion. Thermopower and electrical resistivity of TbNiC2 have been measured in the range of 310–855 K and reveal values characteristic for metallic systems. Seebeck coefficient decreases with increasing temperature approximately linearly in the all studied interval, and its sign changes from positive to negative one at ~660 K, whereby the electrical resistivity increases from 310 K reaching maximum at ~640 K and afterwards decreases slightly. Maximum power factor value of 27 μW m−1 K−2 has been observed at 310 K.