Variation Of Resistivity Research Articles

Nonlinearity in regulating the metal to insulator transition of ReNiO3 towards low temperature range

Among the existing material family of the correlated oxides, the rare earth nickelates (ReNiO3) exhibit broadly adjustable metal to insulator transition (MIT) properties that enables correlated electronic applications, such as thermistors, thermochromics, and logical devices. Nevertheless, how to accurately control the critical temperature (TMIT) of ReNiO3 via the co-occupation of the rare-earth elements is yet worthy to be further explored. Herein, we demonstrate the non-linearity in adjusting the TMIT of ReNiO3 towards lower temperatures via introducing Pr co-occupation within ReNiO3 (e.g., PrxNd1-xNiO3 and PrxSm1-xNiO3) as synthesized by KCl molten-salt assisted high oxygen pressure reaction approach. Although the TMIT is effectively reduced via Pr substitution, it does not strictly follow a linear relationship, in particular, when there is large difference in the ionic radius of the co-occupation rare-earth elements. Furthermore, the most significant deviation in TMIT from the expected linear relationship appears at an equal co-occupation ratio of the two different rare-earth elements, while the abruption in the variation of resistivity across TMIT is also reduced. The present work highlights the importance to use adjacent rare-earth elements with co-occupation ratio away from 1:1 for achieving more linear adjustment in designing the metal to insulator transition properties for ReNiO3.

Enhanced linearity of CaCu3Ti4O12 by changing energy band structure induced by Fe3+ doping for high temperature thermistor application

Polycrystalline oxide materials exhibit semiconductor properties due to grain boundary (GB) and grain characteristics, which enrich the variety of applications. However, how to regulate the energy band structure of grains and the potential barriers at GBs through defect engineering is crucial to achieve a high performance electronic device. Herein, it is found that Fe3+ ions can change the grain energy band structure of CaCu3Ti4O12 (CCTO) materials, which enhances the linearization of the resistance–temperature curve (lnρ–1000/T) in the high temperature region. First principles calculation indicates that Fe3+ doping narrows the forbidden band and induces new impurity energy levels in the forbidden band, which matches the conclusion that the resistivity–temperature dependence of grains shifts toward the low-temperature region as derived from impedance spectroscopy. This shift results in no monotonic variation in grain resistivity within the application temperature region, thus enhancing the linearity of the lnρ–1000/T curve of CCTO materials in the high temperature region. In addition, Fe3+ ions can modulate the activation energy of CCTO materials in a wide range by changing the activation energy of GBs, which broadens the temperature range of CCTO. The significance of this work lies not only in achieving linearization of CCTO materials for high temperature thermistor application, but more importantly, the method presented here provides an avenue for the study of polycrystalline semiconductor materials.

Study on Detection of the Bearing Stratum Integrity of Bored Pile Based on Transient Electromagnetic Method

To ensure the safe construction of bridge pile foundation in karst area, it is necessary to accurately detect the unfavorable geological conditions such as karst cave and soft layer before excavation. In this paper, the transient electromagnetic method is used to probe the geological conditions near the pile Y1 of an interworking main bridge in China’s Hunan Province. By arranging 5 measuring lines at the pile Y1, the voltage variation laws of 21 monitoring points on each measuring line are obtained, and the resistivity variation cloud maps at the measuring line positions are inversed. The results show that the voltage signals at line 1 and line 5 are obviously abnormal, and the resistivity varies greatly within 50 m underground depth, which indicates that there may be adverse geological conditions such as karst cave and carbonaceous limestone interlayer. Further, through on-site hole digging and sampling, it is found that the slag sample in the area above 50 m of the stratum of pile Y1 is wet, and the slag sample below 50 m is dry without argillaceous interlayer, which verifies the effectiveness of transient electromagnetic detection method. Because the transient electromagnetic detection technology does not need drilling and the detection process is convenient, it may provide a new means for quickly detecting the integrity of the bearing layer of bored cast-in-place pile in bridge construction.

Depicting of groundwater potential in hard rocks of southwestern Saudi Arabia using the vertical electrical sounding approach

In the hard rock terrains of southwestern Saudi Arabia, vertical electrical soundings (VES) were used to demarcate groundwater potential zones. To map the groundwater potential zones, 16 VES were done using a Schlumberger electrode array arrangement. Zond-IP computer software was used to analyze and interpret field measurements. The pseudo and resistivity cross-sections have been processed. The evaluation of the 1D geoelectrical curves revealed that the area is characterized by three geoelectrical resistivity layers. The topmost layer of unconsolidated alluvium deposits, which has a wide range of resistivities (42.28 to 297.97 Ω·m) and a thickness of up to 6 m, is the first of these layers. This range of resistivity is linked to changes in the layer's lithology and humidity. The second layer's resistivity values range from 372 to 3625 Ω·m, while the third layer's resistivity values range from 1015.37 to 21113 Ω·m. The second layer's resistivity implies fractured and weathered/jointed basement rocks, and the third layer's resistivity indicates broken to huge basement rocks. According to the findings, the worn and fractured horizons of basement rocks found in the vicinity are acceptable groundwater potential aquifers. The degree of weathering and fracture of the foundation rocks, and thus their water saturation, can be linked to vertical and horizontal variations in resistivity.

Effects of Soil Resistivity Variation with Depth on Crop Yield in a Typical Sedimentary Terrain, Igieduma-Edo State, Nigeria: A Geophysical Method Application in Agricultural Practice

Accurate knowledge of soil fertility is required to promote global food security for life sustenance. Literatures have shown that electrical resistivity method is effective for agricultural site selection without passing through the rigor of soil test. However, the factor responsible for inconsistence in resistivity signature with soil fertility from one place to another, effect of soil texture and depth variation on crop yield are the questions this work geared at providing answers. Ten Vertical Electrical Sounding (VES) were conducted across the study area using Schlumberger array. Res1Dinvers was used for the inversion model, using Least Square method. Twenty soil samples were obtained in the VES points, two samples per point. One sample each at first and second layer. Result of the apparent resistivity showed that areas with high-excellent crop yield have resistivity signature above 500 Ωm while areas with low yield are characterized by values less than 500 Ωm. In both areas of low and high-excellent crop yield, the result of geochemical analysis indicated that Nitrogen, phosphate, and Potassium varied as 59-61%, 43-54mg/kg and 49-51mg/kg, respectively except for organic matter content that was above 3.8% in the first layer have high-excellent yield while low yield soil showed less than 3.8% in their first layer and even if the second layer’s organic matter is above 3.8%. This study has shown that organic matter has significant effect on soil resistivity signature than others soil nutrients (Phosphate, Potassium and Nitrogen). The study shows that soil’s first layer (0-0.3m) is the most suitable depth conducive for soil minerals occurrence for optimum agricultural output.

Unearthing Underground Mining–Induced Strata Disturbance by Electrical Resistivity Tomography Interpretation

ABSTRACT The focus of the study was to evaluate the rock strata transformation above an underground mine panel during pre-and-post mining based on an electrical resistivity tomography (ERT) geophysical technique. The data were acquired using two electrode arrays (i.e., pole-dipole and Wenner-Schlumberger [WS]) with electrode spacing of 6 m up to 570 m in length. The resistivity data were digitally processed through RES2DINV software. The formation of fractured rock in the overburden caused by underground mining operations was clearly distinguished by resistivity anomalies observed using the pole-dipole array. Variation in the hydrogeological condition in the strata was also assessed during the pre-and-post mining conditions. The impact of compression and tension generated in the strata as a result of extraction of coal and subsidence in the overburden rock was observed through prominent resistivity variations observed in an inversion modelling of the WS true resistivity profile. The influence of surface topography in the near surface top weathered rock was also distinctly outlined by the resistivity measurements. ERT is a strong tool capable of providing valuable information regarding strata deformation caused by mining.

Inverse algorithm for extraction of multiple parameters using analytical model of eddy current response

Eddy current (EC) technology is commonly used for detecting flaws, measuring geometric parameters, or determining properties of conducting materials. However, the measurement of a particular parameter can become more challenging if multiple influential parameters vary simultaneously. In particular, eddy current-based measurement of separation (gap) between a pressure tube (PT) and a calandria tube (CT) in the fuel channels of CANDU® reactors is made more difficult by variations in PT wall thickness, resistivity, and probe lift-off. An analytical model of the EC response to changes in PT–CT gap has been developed by approximating the geometry of the PT within the larger diameter CT as a pair of concentric tubes, where gap is varied by changing the CT radius. In this article, this model is used in combination with an error minimization algorithm to construct an inverse algorithm for the extraction of PT–CT gap, PT resistivity (ρ), and PT wall thickness (WT) from measured multi-frequency eddy current signals. Application of a linear regression tool in MATLAB, with fourth-order polynomial fitting of modeled data with varying ρ and WT as a function of PT–CT gap, is used to obtain coefficients that depend on ρ and WT. Output of multidimensional fitting of these coefficients is scaled and rotated to calibration data. Finally, implementation of an error minimization algorithm in MATLAB is used to produce estimates of multiple target parameters from experimental data. Simultaneous extraction of either one, two, or three parameters is examined, using experimental data obtained at frequencies used for in-reactor inspection of 4.2, 8, and 16 kHz, or just two frequencies of 4.2 and 8 kHz. Under full gap variation conditions, the inverse algorithm predicts gap to within 0.1 mm at gaps between 0 and 9 mm and to within 0.4 mm at gaps between 9 and 18 mm. PT resistivity is predicted to within 1 μΩ cm (2% relative error) and PT wall thickness within 0.03 mm (1% relative error) when each is the only extracted parameter. An excellent agreement between actual and predicted values of gap demonstrates the potential of the inverse algorithm for application to in-reactor gap measurement and simultaneous extraction of either PT wall thickness or resistivity when the other parameter is known. The extraction of PT resistivity may be particularly useful, as this parameter cannot otherwise currently be measured in-reactor.

Upgrading of a Technique for Visual Comparing for the Results of Azimuthal Magnetotelluric Monitoring with the Seismic Events Parameters

The paper presents a practical implementation of the task of visualizing additional geophysical information for analyzing the results of azimuthal magnetotelluric (MT) monitoring. Since some patterns of a sharp change in the sign of relative apparent resistivity variations (Δρ) for MT monitoring points depending on ongoing seismic events, as well as lunar-solar tides, were found in previous studies, it became necessary to give illustrative examples proving such cases. For this, we propose to improve the technique for constructing additional graphs containing such parameters of seismic events as: source depth, distance between the source and the observation point, azimuth and energy class, in accordance with the observation time. All parameters are obtained from published seismic catalogs. A method for displaying pseudosections Δρ, combined with a hypocenter distribution plot, in Surfer program is shown. An example of a graph containing simultaneously information about the distance and azimuth of the event relative to the monitoring point, in the form of rotated arrows, is given. Such graphical constructions are maximally automated, and allow the interpreter to confirm the arguments in favor of the spatial-temporal dependence of the variations of electromagnetic parameters on the events occurring in the observed earth's interior.

Structural, dielectric, and electrical transport properties of Al3+ substituted nanocrystalline Ni-Cu spinel ferrites prepared through the sol–gel route

In this study, a series of nanocrystalline Ni0.7Cu0.30AlxFe2-xO4 (x = 0.00 to 0.10 with a step of 0.02) has been synthesized through the sol–gel auto combustion technique. The structural, morphological, dielectric, and electrical properties of the synthesized nanoparticles are analyzed due to the substitution effect of Al3+ content. The structural study has been performed through the XRD and FTIR analyses. The extracted XRD patterns assure the single-phase cubic spinel structure of all samples in high crystalline nature with maintaining their homogeneity. The average crystallite size of the nanoparticles is found in the range of 55.63–70.74 nm, and the average grain size varies from 59.00 to 65.00 nm. FTIR study also confirms the formation of spinel structures in the prepared Ni-Cu ferrite nanoparticles. The surface morphology of the materials has been studied through the FESEM study linked with EDX analysis. The dielectric dispersion of the materials is reflected at lower frequencies up to 10 kHz. The impedance spectroscopy confirms the non-Debye relaxation phenomena of the synthesized nanomaterials. The contribution of grains and grain boundaries is resolved through the modulus study of the materials. The trend in variation of AC resistivity with frequency has been explained by the hopping mechanism.

Time-lapse adaptive inversion on resistivity monitoring data with Lp norm regularization and cross-time weight

Time-lapse electrical resistivity tomography (ERT) can describe the dynamic processes occurring underground and has been widely employed in the fields of hydrology, environmental management, and engineering. The time-lapse inversion method is based on the space- and time-dimension regularization technique as it considers complementary information about more than one time interval and reduces the potential causes of the geophysical data inversion of the artifact. However, the L2 norm inversions smear out the models and cannot distinguish between the resistivity interfaces. Moreover, the determination of the two optimal regularization parameters for time-lapse inversion remains challenging, and the fixed-time regularization parameter smooths out the low-sensitivity area and inhibits the real variation on the target body of the deep region. To overcome this problem, we propose a time-lapse ERT inversion method of adaptively imaging the time-lapse model and focusing on the resistivity variation on the time dimension. This method is based on the Lp norm regularization provided by the M-estimator and uses the adaptive regularization parameters based on the model roughness and data misfit. In addition, a cross-time matrix improving the sensitivity in the deep region of model space is added to the time regularization term. We present two synthetic examples and a field dataset to validate the method. Numerical simulation and field dataset inversion results revealed that the proposed time-lapse inversion strategy can avoid the excessive smoothness caused by the low sensitivity in the model deep region and can thus enhance the response from the true ground variation to improve the accuracy of the inversion results. Owing to the adaptive regularization parameters that can preserve the dynamic balance between the objective function components, the inversion iteration progress can remain stable and can maintain the trend toward convergence.

Effects of damage on resistivity response and volatility of water-bearing coal

A series of experimental geophysical methods with resistivity as the key parameter provide strong support for predicting and providing early warnings of geological disasters. In this study, coal samples with similar P-wave velocities and pore distributions were screened, and a weighing method was used to control the water content of the coal samples. A real-time test system was independently constructed to conduct uniaxial compression tests on these coal samples and synchronously monitor resistivity and acoustic emission (AE) data. The results show that resistivity obviously characterizes the process of coal failure under load. The development of microfractures causes fluctuations. The resistivity changes relatively smoothly before the development of fractures, and resistivity fluctuations are obvious during the development of fractures. The resistivity fluctuation range reaches the maximum when the whole fracture occurs at the stress peak, but the presence of water weakens the resistivity fluctuations during the whole process of failure. Water migration causes circuit reconnection and changes the fluctuations. With increasing water content, the uniaxial compressive strength (UCS), elastic modulus (E) and maximum AE amplitude decrease. The resistivity variation at the peak value also decreases. Under the condition of 9.2% water content, the resistivity variation at the peak stress is only 2.52%. The results prove that violent fluctuations of resistivity correspond to the development of microfractures in the sample, and the amplitude of the fluctuations is positively correlated with the degree of damage and fracture. The volatility index (Resistivity Standard Deviation, RSD) is established to describe the degree of resistivity fluctuation, and the peak value occurs when the AE energy increases sharply. The establishment of a volatility index aims to provide a new parameter for rock damage and dynamic disaster prediction technology.

Soil Treatment to Reduce Grounding Resistance by Applying Low-Resistivity Material (LRM) Implemented in Different Grounding Systems Configurations and in Soils with Different Resistivities

In the present study, field tests were performed using low-resistivity materials (LRMs) in different grounding system (GS) configurations to reduce the grounding resistance (GR) and assess the variation in the effectiveness of the LRMs with increases in the complexity of the GS design. Different configurations were implemented in soils with different resistivity values to determine the variation in the effectiveness of each LRM design with increases in the soil resistivity. Lastly, the percentage decrease in the GR was assessed as a function of the increase in the complexity of the GS design and the variation in the soil resistivity. The results of this study provide a useful guide for engineers and researchers who study, design, and build innovative and effective GSs by applying improved compounds for safe electrical installations.

Research Progress on Global Marine Gas Hydrate Resistivity Logging and Electrical Property Experiments

Natural gas hydrate is widely spread in marine environments around the world. It has great energy potential due to its high methane gas content. High-precision exploration and evaluation of marine gas hydrate still face great challenges as it is affected by the complex reservoir control mechanisms and distribution characteristics. Resistivity is widely used in geophysical logging and theoretical research on gas hydrate-bearing reservoirs by utilizing the high sensitivity electrical response. In this paper, based on the examination of the global marine gas hydrate occurrences, resistivity logging results are summarized. Then the key remaining gas hydrate resistivity experimental concerns are reviewed. In summary, resistivity properties are a reliable means to derive the gas hydrate reservoir characteristics, despite the effect induced by the anisotropic properties of hydrate reservoirs and drilling technology. The overall resistivity change associated with the occurrence of pore filling gas hydrate in reservoirs are relatively small, and the specific value is affected by sediment lithology and hydrate saturation. On the other hand, fracture filling hydrate reservoirs have strong anisotropy, and massive hydrate occurrences (i.e., layers of gas hydrate with no sediment) section shows very high resistivity variation. Clay minerals are an important factor restricting the accurate estimation of gas hydrate saturations from in situ resistivity measurements. Many experimental studies have proposed the correction of Archie empirical formula, but widely representative models have not yet been developed. It is worth noting that more complex resistivity measurements may be able to provide additional electrical response information on various gas hydrate systems.

Groundwater exploration using vertical electrical sounding techniques in parts of Etche Local Government Area of Rivers State, Nigeria

Vertical Electrical Sounding (VES) was carried out in parts of Etche Local Government Area, Rivers State, Nigeria to investigate availability of groundwater. An ABEM SAS 1000 terrameter was used. Schlumberger configuration was adopted for the sounding to acquire a 4 point data, with the use of ID Interpex software in order to know the subsurface variations in resistivity with respect to depth. The investigation revealed the subsurface, thickness of lithology, prolific aquiferous zones, the resistivity curve portrays an overall increase in resistivity trend ranging from 228.7Ωm - 5872Ωm. The resistivity trend in the form of ρ1< ρ2< ρ3< ρ4< ρ5, indicates the presence of conductive materials present at a shallow depth of the point of survey. The highest resistivity value is observed in the fifth layer and it is believed to have gravely sized particles. A stratigraphic layer with gravely sized particles in this area revealed a good aquifer quality with reasonable quantity of aquifer fluid contained within the interconnected pore spaces. This zone of the studied area contains rock units from the geoelectric section such as silt, medium sand, coarse sand and gravel. The fifth layer is the prospect zone for aquifer delineation. A geoelectric section drawn from the resistivity data shows that the first layer is silt, the second layer is fine sand, the third layer is medium sand, the fourth layer is silty sand, the fifth layer is fine sand and the sixth layer is medium sand. The sixth layer is believed to be the prospect zone for aquifer characterization. A suitable data from drilled boreholes should be introduced to this study so as to have a profound knowledge and views about the grain size, sphericity, roundness and parking. These characteristics will be useful to determine the dominant grain size existing in these aquifers and characterize them appropriately.

Application of Multi-Channel Analysis Surface Waves and Electrical Resistivity Tomography Methods to Identify Weak Zones at University of Mosul, Northern Iraq

Cracks have been developed in a large lecture hall on the University of Mosul Campus. These cracks exist along two sides of the building. Multi Analysis Surface Wave and Electrical Resistivity Tomography surveys were conducted at the surrounding building to investigate the nature and distribution of shallow subsurface soil/rock. The MASW’s data show three layers: the first layer is characterized by low shear wave velocity ranges between 210 and 420 m/s which is attributed to infill materials, the next layer is attributed to a river terrace (fairly competent rock) which has Vs ranging from 430m/s to 840 m/s. It is recognized by a gradual increase in mechanical characteristics as depth increases. In-depth between about 2.5m and 6.0 m the shear wave velocity drops in the top contact of this layer. The causes of low velocity may be due to weathering of the medium because of a sinkhole. The Electrical Resistivity Tomography profile shows four electrical zones, the first zone has 50-70 Ω.m. with a variable thickness from 0.5-1.5 m which indicates infill materials. The second zone has very low resistivity value, and a depth ranges 0.5m - 3.5 m, which might be interpreted to be increased clay, silt and water content (high water-saturated zone). The third zone is characterized by a high-resistivity value (>100 Ω.m) that could be related to a dry conglomerate rock and gravels belong to river terraces. The fourth zone has a low-resistivity value (<20 Ω.m) associated with a water-saturated marl bed. We could be definitively correlated the resistivity and velocity anomalies to sinkhole activity in were identified and characterized using combined geophysical methods. The Multi Analysis Surface Waves and Electrical Resistivity Tomography were shown to complete each other in the evaluation. The variations in Vs (low velocity) and resistivity (conductive zone) within the river terrace were detected and proposed to be indicative of dissolution and the subsidence responsible for structural damage implied by the change in the velocity and resistivity. The roughness of the top terrace surface strongly influences the nature of the velocity and resistivity values. This roughness is suggestive of dissolution or erosion.

IDENTIFIKASI AIR TANAH MENGGUNAKAN METODE GEOLISTRIK DI KECAMATAN POMALAA KABUPATEN KOLAKA PROPINSI SULAWESI TENGGARA

ABSTRACTThis research is motivated by development and population growth continues to increase from day to day. The impact of population growth is the increase in residential land. The increase in residential land is sometimes not accompanied by the provision of clean water by PDAM, so that people use dug wells or drilled wells. In the Kolaka area, especially the Kolaka District area, which is the research location, it is also a location that is difficult to find fresh water, so the geoelectric method plays a very important role in efforts to determine which locations contain fresh water. This research uses resistivity geoelectric method with Wenner and Schlumberger configuration. Processing data using Res2Dinv to map 2D isoresistivity. The well depth data was processed using Microsoft Excel, Surfer 10.2 application and ArcGIS to create a groundwater network map. The measurement trajectory uses a space of 7 meters, 20 meters and 40 meters. The results of the study obtained different resistivity values for each rock. The resistivity variation obtained starts from 0.453 – 13,988 m. Groundwater resistivity values are in the range of resistivity values of 0.453 – 33.3 m. The lithology of the aquifers in the study area is alluvial and sandstone. In the research location, groundwater is generally found at a depth of more than 5 meters

Coexisting ferromagnetic component and negative magnetoresistance at low temperature in single crystals of the VdW material GaGeTe

We report magnetoresistance and magnetization studies of single-crystal GaGeTe, which has been proposed as a Van der Waals material. Semi-metallic character is observed in the temperature (T) variation of resistivity (ρ), following ρ(T) ​∝ ​T2 ​at low temperature with a slope compatible with the usual spin-fluctuating system. Magnetoresistance (MR) at 2 ​K is negative and strongly dependent on the direction of the magnetic field (H) with respect to the crystallographic c-axis. MR changes sign with increasing temperature above ∼ 100 ​K, when H is applied along the c-axis. Hall measurements indicate the p-type conductivity with a considerable hole concentration of ∼ 8.7 ​× ​1019 ​cm−3. Angle-resolved photoemission spectroscopy reproduces the reported results and confirms a peculiar dispersion shape of the hole-like band at the bulk high-symmetry T point near the Fermi energy indicating band inversion. Magnetic hysteresis measurement at 2 ​K shows diamagnetic behaviour at high-H, whereas a ferromagnetic (FM)-like magnetic hysteresis loop is observed at low-H in between ​± ​4 ​kOe. The FM component disappears close to 3 ​K. Signature of spin-fluctuation in ρ(T), negative MR, and low-T FM component without 3d or 4f impurities in GaGeTe is attractive for the fundamental interest.

Study on Road Performance and Electrothermal Performance of Poured Conductive Asphalt Concrete

In order to realize the active melting of ice and snow of poured asphalt concrete on steel bridge deck pavement in winter, graphite and carbon fiber were selected as conductive materials to prepare poured conductive asphalt concrete CGA-10. The influence of the content of conductive phase material on the electrical resistivity variation of poured conductive asphalt concrete was studied. The influence of conductive materials and their content on pavement performance of poured conductive asphalt concrete was analyzed. The heating effect of poured conductive asphalt concrete was studied. And the ice melting efficiency of poured conductive asphalt concrete was evaluated by indoor deicing test. Finally, the microstructure characteristics were analyzed by SEM. Experimental results showed: 0.4% carbon fiber +30% graphite can form a good conductive network in poured conductive asphalt concrete. Carbon fiber can make up for the adverse effect of graphite on the pavement performance of poured conductive asphalt concrete. Heating efficiency of 0.4% carbon fiber +30% graphite poured conductive asphalt concrete can reach 78.85%, and its ice melting efficiency can reach 50.03%. Graphite powder particles are tightly wrapped with asphalt mortar, which reduces the porosity and resistivity of asphalt mixture. On the one hand, carbon fiber makes up for the interruption of graphite particle conductive chain, on the other hand, it plays a reinforcing role.

Electrical, Optical, and Structural Stability Over Ten Years for Sb Based III-V Semiconducting Bulk Grown by VDS

III-V semiconductors have an advantage of not being degraded with time at room temperature, among non-silica semiconductors. This stability property is useful at the places where frequent device replacement is not possible. Determination of stability parameters are needed to be studied prior to their application as a junction substrate. The Vertical Directional Solidification (VDS) technique is employed for the growth of bulk crystals, without the seed, without contact to the ampoule wall, without coating, and without external pressure. The antimony based III-V substrates have been studied before and after an interval of ten years for any possible degradation in quality that may affect their applicability. XRF, EDAX, FTIR, XRD, Raman, and resistivity measurements methods were used to measure compositional optical, structural, and electrical consistency over the time. These bulk crystals revealed a high degree of stability within experimental limits for more than ten years, including intact crystalline structure, no formation of oxides, compositional stability, and no significant variation in band gap and resistivity, and hence still appropriate to be applied in semiconductor junction fabrications.

Investigation Into Variation of Resistivity and Permittivity of Aqueous Solutions and Soils With Frequency and Current Density

Soil parameter characterization and the variation of permittivity and resistivity with frequency (dispersion) and current density have been the subject of many experimental studies but significant differences in measured values are found in the literature due to different testing approaches, apparatus, and test sample composition. This article first presents a comprehensive review of this previous body of work. Then, new experiments on soils and electrolytes with test frequencies in the range 1 Hz to 10 MHz and with current densities from 1 to 35 mA/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> are described. Such results help clarify the effects of frequency, soil moisture, electrolyte concentration, and electrode material on the measured test medium parameters. The contribution of the electrode-electrolyte interface (EEI) and the influence of current density are particularly highlighted. These findings indicate that some previous measurements may have overestimated the measured values of resistivity and permittivity due to the EEI effect. Finally, the test results are compared with soil parameter equations from CIGRE TB781.