Temperature Dependence Of Electrical Parameters Research Articles

Dielectric, magnetic and electrical properties of ZnFe2O4 ceramics

The polycrystalline sample of ZnFe2O4 was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction studies of the compound showed the formation of a single-phase compound at room temperature. Studies of dielectric properties (er, tan δ) of the above compound as a function of frequency in a wide temperature range show dielectric anomalies signifying existence of possible ferroelectric to paraelectric phase transition in the material. The confirmation of this assumption was made with observation of ferroelectric hysteresis loop at room temperature. Magnetic measurement exhibits anti-ferromagnetic nature of the sample. Studies of the zero-field cooled and the field-cooled magnetization in dc field provided the blocking temperature TB. The temperature dependence of electrical parameters (impedance, modulus, conductivity, etc.) of the material exhibits a strong correlation between the microstructure (i.e., bulk, grain boundary, etc.) and electrical parameters of the material. Detailed studies of impedance parameters have provided an insight into the electrical properties and understanding of types of relaxation process in the material. The temperature variation of dc resistivity/conductivity exhibits negative temperature coefficient of resistance behaviour of the material. The frequency dependence of ac conductivity suggests that the material obeys Jonscher’s universal power law.

Electrical and pyroelectric properties of lanthanum based niobate

A lanthanum based new tungsten bronze (TB) ferroelectrics (K2Pb2La2W2Ti4Nb4O30) was synthesized by a mixed-oxide method at high temperature. Thermogravimetry analysis (TG) technique was used to decide the material preparation conditions. The formation of desired compound was confirmed by preliminary X-ray structural analysis. The SEM micrograph of the sintered sample exhibits uniform rod-like grain distribution without many voids. Detailed studies of the nature of variation of dielectric parameters with temperature and frequency shows dielectric anomaly at 310°C. The temperature dependence of electrical parameters (impedance, modulus, conductivity, etc) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc) and electrical properties. The dc conductivity follows the Arrhenius equation, and thus its variation with rise in temperature reveals the negative temperature coefficient of resistance (NTCR) behavior of the material. The material obeys Jonscher's universal power law which is evident from the frequency dependence of ac conductivity. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit. Hence the material is useful for pyroelectric sensors.

SYNTHESIS AND CHARACTERIZATION OF COMPLEX FERROELECTRIC OXIDE

The polycrystalline sample of Li2Pb2Pr2W2Ti4V4O30 was prepared by a solid-state reaction technique. The preparation conditions of the compound have been optimized using thermal analysis (DTA and TGA) technique. Room temperature structural analysis confirms the formation of single phase compound in orthorhombic crystal system. The surface morphology of the sample, recorded by scanning electron microscope, shows uniform grain distribution on the surface of the sample. The observation of hysteresis loop confirmed that the material has ferroelectric properties at room temperature. Electrical properties of the material were studied by complex impedance spectroscopic technique. Temperature dependence of electrical parameters (impedance, modulus, etc.) is strongly correlated to the micro-structural characteristics (bulk, grain boundary, etc.) of the sample. A typical temperature-dependent resistive characteristic of the sample (i.e., negative temperature coefficient of resistance (NTCR)) exhibits its semiconducting properties. The temperature dependence of dc conductivity shows a typical Arrhenius behavior. A signature of ionic conductivity in the system was observed in ac conductivity spectrum. The sample obeys Jonscher's universal power law. The hopping mechanism for electrical transport properties of the system with nonexponential-type conductivity relaxation was suggested from the electrical modulus analysis.

Structural, dielectric and electrical properties of dysprosium based new complex electroceramics

The polycrystalline sample of K2Pb2Dy2W2Ti4Nb4O30 was synthesized by high—temperature solid—state reaction method (calcinations temperature ~1,050 °C and sintering temperature ~1,075 °C). The phase formation of the desired compound was confirmed by preliminary X-ray structural analysis. The scanning electron micrograph shows uniform plate and rod like grain distribution throughout the surface of the sample without much pores. Detailed studies of the nature of (1) variation of dielectric parameters with temperature (27–480 °C) and frequency (1 kHz–5 MHz) and (2) polarization (at three different temperatures) confirmed the existence of ferroelectricity in the material, with phase transition occurring at 316 °C. The temperature dependence of electrical parameters (impedance, modulus, conductivity, etc.) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc.) and electrical properties. The nature of temperature dependent dc conductivity follows the Arrhenius equation, and reveals the negative temperature coefficient of resistance (NTCR) behaviour of the material. The material obeys Jonscher’s universal power law which is evident from the graphs of frequency dependence of ac conductivity.

Temperature Modulation of Electric Fields in Biological Matter

Pulsed electric fields (PEF) have become an important minimally invasive surgical technology for various applications including genetic engineering, electrochemotherapy and tissue ablation. This study explores the hypothesis that temperature dependent electrical parameters of tissue can be used to modulate the outcome of PEF protocols, providing a new means for controlling and optimizing this minimally invasive surgical procedure. This study investigates two different applications of cooling temperatures applied during PEF. The first case utilizes an electrode which simultaneously delivers pulsed electric fields and cooling temperatures. The subsequent results demonstrate that changes in electrical properties due to temperature produced by this configuration can substantially magnify and confine the electric fields in the cooled regions while almost eliminating electric fields in surrounding regions. This method can be used to increase precision in the PEF procedure, and eliminate muscle contractions and damage to adjacent tissues. The second configuration considered introduces a third probe that is not electrically active and only applies cooling boundary conditions. This second study demonstrates that in this probe configuration the temperature induced changes in electrical properties of tissue substantially reduce the electric fields in the cooled regions. This novel treatment can potentially be used to protect sensitive tissues from the effect of the PEF. Perhaps the most important conclusion of this investigation is that temperature is a powerful and accessible mechanism to modulate and control electric fields in biological tissues and can therefore be used to optimize and control PEF treatments.

Characterization and Analysis of the Temperature-Dependent on -Resistance in AlGaN/GaN Lateral Field-Effect Rectifiers

The on-resistance and its temperature dependence of the high electron mobility transistor (HEMT)-compatible lateral field-effect rectifier (L-FER) are investigated. Three types of transfer length method (TLM) patterns are utilized to extract the temperature-dependent electrical parameters of the resistance model. The technique presented in this paper delivers a direct and simple methodology for the investigation of the temperature dependence of the on-resistance in the L-FER. The simulated output characteristics of the L-FER are in good agreement with the experimental results.

High-temperature electric conductivity of some feldspars

Feldspars are abundant and characterized by diversity of chemical composition, as well as crystallochemical peculiarities of the phase and structural states. This mineral occupies an important place in the classification of magmatic rocks owing to the possibility of its application as the most informative material: as an indicator of the crystallization conditions and evolution of different rocks [1, 2]. The main typomorphic indicators of feldspars are their composition, ordering of Si and Al atoms in the Si‐Al‐O framework, and processes of inverse transitions [3‐5]. Many studies (overviews included) devoted to feldspars are available in the scientific literature [1‐5]. Nevertheless, typomorphism of feldspars remains a pressing issue. The properties of minerals with genetic information are diverse (optical, luminescent, thermal, and others). Electric properties (including high-temperature properties that carry information about crystallochemical features of the phase and structural states of the matter) can occupy an important place in this respect. However, information about the temperature dependence of electric parameters of feldspars is very limited [6‐8].

Comparison of constant current and pulsed gas metal arc welding processes on basis of electrode resistive dissipation

The dependence of electrode electrical parameters (resistivity and action) on temperature results in a variation of voltage drop along the electrode extension. In the present work, effects and interactions of the temperature dependent electrical parameters in constant current gas metal arc welding and pulsed gas metal arc welding of mild steel are examined and the differences between these two welding processes are determined using the above mentioned electrical parameters, which are calculated based on a resistivity model. The temperature dependent electrical parameters are also used to compute the electrode voltage drop and the arc voltage, which are very difficult to measure directly in practice. Furthermore, the processes are compared using electrode resistive dissipation. Use of the same input in both processes assists in the comparison of the two processes.

A.c. Conductivity behavior of a hot pressed [PbTiO 3–PbZrO 3–PbCuNbO 3] ferroelectric ceramic

The temperature dependence of electric parameters of the sintered compound PbZr 0.5Ti 0.44(Cu 1/4Nb 3/4) 0.06O 3+0.5 mol% MnO 2 was investigated using a.c. measurements. The temperature dependence of the a.c. conductivity in the vicinity of T c is highly non-linear with a local maximum in conductivity observed at that temperature. The total conductivity σ t( ω), as a function of frequency, exhibits a power law dependence ( σ 0+ Aω s ), whose exponent s is maximized at the ferro–paraelectric transition.

Surface layers in PLZT 7/65/35 ceramics

A phenomenological model based on the two-layer capacitor was applied to analyze the temperature dependence of electrical parameters of the surface layers and of the bulk of PLZT 7/65/35 ceramics. The measurements were performed on samples which had electrodes evaporated with silver. A strong temperature dependence of the electrical properties of the surface layers was found. The dielectric permittivity of the surface layers varies from 5 to 240 and their conductivity varies from 0.3 × 10-7 to 3 × 10-7 Ω-1 m-1.

Ion movement relaxation in inorganic glasses — salient features

The movement of (alkali) ions in inorganic glasses shows several general features which cannot be understood from the classical theories for crystals having low mobile ion concentration. These features have been identified from the frequency and temperature dependence of electrical parameters and nuclear spin relaxation and anomalous isotope mass dependence of lithium diffusion in lithium triborate glass. A successful theoretical model is expected to explain various features discussed here including the composition dependence of the observations.

Investigation of some second order effects in SAW devices

The reflections of SAW in SAW devices, the SAW diffraction and the effect of temperature on the parameters of SAW devices are considered. The equivalent circuit model of the interdigital transducer is used to compute the reflections, the efficient fast Fourier transform algorithmus allows rapid computation of the SAW diffraction and the third order elastic stiffnesses and higher order temperature coefficients make possible to compute the temperature dependence of electric parameters of SAW devices.