Showing papers on "Temperature coefficient published in 1977"
TL;DR: In this article, the temperature coefficient of the resistivity of metallic glasses is calculated starting from the same formalism which has been used to calculate the resistivities in liquid transition metals, and an explicit equation is derived for the temperature dependence which includes both effects due to the decrease in the static structure factor and those due to phonons.
Abstract: The temperature coefficient of the resistivity, $\ensuremath{\alpha}$, of metallic glasses is calculated starting from the same formalism which has been used to calculate the resistivity in liquid transition metals. An explicit equation is derived for the temperature dependence which includes both effects due to the decrease in the static structure factor as well as those due to phonons. The magnitude as well as the explicit temperature dependence of $\ensuremath{\alpha}$ is in good agreement with experiment.
197 citations
TL;DR: In this article, the effects of various additive elements on the magnetic properties of quaternary alloys were studied and it was found that zirconium was the best additive element for improvement of their magnetic properties.
Abstract: The effects of various additive elements on the magnetic properties of Sm-Co-Cu-Fe quaternary alloys were studied. It was found that zirconium was the best additive element for improvement of their magnetic properties. The best properties were so far obtained for an alloy of Co, 25.5wt% Sm, 8wt% Cu, 15wt% Fe, 1.5wt% Zr. The energy product of this alloy attains 30MGOe by a step tempering following the solution treatment. In addition to excellent magnetic properties, Sm 2 (Co, Cu, Fe, Zr) 17 type permanent magnets exhibited the desirable temperature coefficient of residual magnetization of 0.03%/°C and a temperature coefficient of intrinsic coercive force of 0.16%/°C.
162 citations
TL;DR: The Evans modification of Ziman liquid-metal theory is extended to apply to amorphous and disordered crystalline alloys as mentioned in this paper, and the theory is shown to explain such common behavior of these systems as the change in sign of the temperature coefficient of resistivity with alloy composition.
Abstract: The Evans modification of Ziman liquid-metal theory is extended to apply to amorphous and disordered crystalline alloys. In particular, the theory is shown to explain such common behavior of these systems as the change in sign of the temperature coefficient of resistivity with alloy composition, the quadratic temperature dependence of resistivity at low temperature, and the linear temperature dependence of resistivity at high temperatures.
131 citations
TL;DR: In this article, the temperature dependence of the electrical resistivity of amorphous metals is calculated using two complementary models of the lattice vibrations, one of which describes uncorrelated Einstein oscillators and the other one leads to a very satisfactory fit of the experimental data for CuSn alloys at T>or approximately=10K.
Abstract: The temperature dependence of the electrical resistivity of amorphous metals is calculated using two complementary models of the lattice vibrations. The model which describes uncorrelated Einstein oscillators leads to a very satisfactory fit of the experimental data for CuSn alloys at T>or approximately=10K. The negative temperature coefficients are explained by the temperature dependence of the elastic scattering. The results are interpreted as an indication of strong vibrational disorder. For very low temperatures (T
78 citations
TL;DR: In this article, pressure-sintered LixNa1−xNbO3 with radial frequency constants fR(r) between 1.75 and 1.95 kHz, coupling coefficients up to 0.4, and permittivities between 100 and 200.
Abstract: Pressure‐sintered LixNa1−xNbO3 in the range 0.015⩽x⩽0.15 exhibits electromechanical properties amenable to high‐frequency device applications with radial‐frequency constants fR(r) between 1.75 and 1.95 kHz m, coupling coefficients up to 0.4, and permittivities between 100 and 200. The temperature and time dependencies of fR are shown to be strongly related to composition, where for x=0.12, the temperature coefficient between −40 and 80 °C is −2×10−4 °C−1 and the ageing coefficient is −2.5×10−3 per decade. The results are discussed in relation to composition and with respect to anomalies at phase transitions in (Li,Na)NbO3.
67 citations
TL;DR: By starting from the Mayadas-Shatzkes model an effective mean free path l g is defined to describe electronic conduction in thin polycrystalline metallic films; the Fuchs-Sondheimer model can then be used to calculate the film resistivity and its temperature coefficient.
63 citations
TL;DR: In this article, the authors measured the elastic constants, temperature coefficients of elastic constants and thermal expansion coefficients in Ba2Si2TiO8 and found that the largest values of k′31 and k′15 are 0.13 and 0.28, respectively, and the minimum value of [Tfr]L is −47 ppm/°C.
Abstract: All the elastic constants, temperature coefficients of elastic constants, and thermal‐expansion coefficients in Ba2Si2TiO8 were measured. Signs of the piezoelectric constants d31 and d15 were determined to be positive. From the calculations of the orientational dependences on the electromechanical coupling factors k′31 and k′15 and the temperature coefficient of resonance frequency [Tfr]L in the length‐extensional mode, it was found that the largest values of k′31 and k′15 are 0.13 and 0.28, respectively, and the minimum value of [Tfr]L is −47 ppm/°C. Surface‐acoustic‐wave analysis for the crystal showed that the SH‐mode piezoelectric surface wave has a piezoelectric coupling constant, k2=0.0053, larger than that of quartz, and a temperature coefficient of delay Tτ=+38 ppm/°C for the Y‐propagation direction on the X‐cut surface, smaller than that of LiNbO3.
52 citations
TL;DR: The thickness dependence of the temperature coefficient of resistivity of polycrystalline metal films is given by approximate Mayadas-Shatzkes expressions using the grain intrinsic mean free path of the conduction electrons as mentioned in this paper.
47 citations
TL;DR: In this article, the non-coincidence of the experimental temperature coefficient of the potential of zero charge with the water dipole contribution to the electrode potential is demonstrated and discussed.
40 citations
TL;DR: In this paper, in situ measurements of Hall effect, magnetoresistance, resistivity, and temperature coefficient of resistivity of bismuth films (700-2600 A) were carried out in a specially designed evacuation chamber.
Abstract: In situ measurements of Hall effect, magnetoresistance, resistivity, and temperature coefficient of resistivity of bismuth films (700–2600 A) were carried out in a specially designed evacuation chamber. The films were deposited on a glass substrate at 150°C and at a pressure of ∼10−6 Torr. The values of the mean free path and specular scattering parameter obtained were 14100 A and 0.5, respectively. The effect of the grain boundary on the electrical resistivity was also accounted for in the light of the Mayadas‐Shatzkes theory.
40 citations
TL;DR: In this article, exact analytical expressions for the temperature coefficient of resistivity for monocrystalline and polycrystalline films were calculated starting from the Mayadas-Shatzkes equations for film conductivity.
TL;DR: In this article, the microwave dielectric constant and loss tangent of Cr-doped semi-insulatiug GaAs have been measured in the frequency range 2.5-36.0 GHz.
Abstract: The microwave dielectric constant and loss tangent of Cr-doped semi-insulatiug GaAs have been measured in the frequency range 2.5-36.0 GHz and the temperature range 300-400 K. The room temperature dielectric constant is 12.95 and the temperature coefficient alpha ( /spl equiv/ epsilon(0)/sup -1/ d epsilon/dT) is 1.6 x 10/sup -4/ /K. The dielectric constant and loss tangent of CdTe have been measured as functions of temperature at 15.95 GHz. The room temperature dielectric constant is 10.39 /spl plusmn/ 0.04 and the temperature coefficient alpha is 2.5 x 10/sup -4/ /K.
TL;DR: In this paper, the electrical resistivity and temperature coefficient of resistivity of tin films (490 to 5000 A) deposited onto glass substrates at room temperature (30° C) were measured in situ in the temperature range 30 to 150° C.
Abstract: The electrical resistivity and the temperature coefficient of resistivity of tin films (490 to 5000 A) deposited onto glass substrates at room temperature (30° C) were measured in situ in the temperature range 30 to 150° C. It is concluded that Mayadas-Shatzkes theory reproduces the experimental observations more faithfully than Fuchs-Sondheimer's theory.
TL;DR: In this paper, the preferential evaporation rate of germanium oxide from solid garnet as a function of temperature and oxygen partial pressure was determined, and the compositional range of melts that form a single garnet phase on solidification was determined by differential thermal analysis.
Patent•
14 Jan 1977
TL;DR: In this article, a positive temperature coefficient heater for enhancing the response time of thermal actuators is disclosed, which is formed of a generally low resistance material that has an anomaly temperature above which the resistance of the heater increases dramatically.
Abstract: A positive temperature coefficient heater for enhancing the response time of thermal actuators is disclosed. The PTC heater is formed of a generally low resistance material that has an anomaly temperature above which the resistance of the heater increases dramatically. The anomaly temperature is chosen to substantially match the phase change temperature of a thermally expansive medium useful to power the actuator. The heater is self-regulating and provides a maximum surface area for heating the medium rapidly with a minimum of thermal mass and energy use. Preferably, the heater is formed of doped BaTiO3 in the general shape of an elongated annular cylinder.
TL;DR: In this article, a gradual conductivity transition as the atomic composition (X) of Hg/Xe samples is varied at 6 K has been observed, interpreted in terms of a Mott-Anderson metal-nonmetal transition smeared out by thermally activated hopping.
TL;DR: In this article, it was shown that polyamide-metal compositions can be classified as semiconductors by using temperature-resistivity dependence and a negative temperature coefficient of the resistivity.
Abstract: It was expected that elemental copper or zinc introduced into polycaproamide would interact with amide groups of the polymer and that the materials would be characterized by semiconductor properties. To prove this theory, resistivity at several temperatures was determined and thermal activation energies calculated. As the metal contents were relatively low, metallic conductivity was avoided. Temperature-resistivity dependence and a negative temperature coefficient of the resistivity prove that polyamide–metal compositions can be classified as semiconductors.
TL;DR: In this paper, the thermoelectric power of systematically annealed silver films (170-1300 A) in the temperature range from -160 °C to the annealing temperature of the film was studied.
Patent•
21 Feb 1977
TL;DR: In this paper, a level detector is designed to detect a liquid by a change in the resistivities which is caused by a difference in the temperatures in a liquid phase and a gas phase, when a thermistor having a temperature coefficient generates heat by itself.
Abstract: PURPOSE:In a level detector which detects a liquid by a change in the resistivities which is caused by a difference in the temperatures in a liquid phase and a gas phase, when a thermistor having a temperature coefficient generates heat by itself, the level detector is designed to detect a liqid lavel in a wide renge of the temperatures used, by connecting in series temperature compensating thermistors having a temperature coefficient reverse to each other.
01 Mar 1977-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: The positive temperature coefficient of the surface tension of molten zinc has been confirmed experimentally with a maximum-bubble-pressure (MBP) system in this article, where the measurements were made on 99.999 pct zinc in the range from 436 to 806°C in an improved twin-tube MBP system.
Abstract: The positive temperature coefficient of the surface tension of molten zinc has been confirmed experimentally with a maximum-bubble-pressure (MBP) system. The possible effects of the high vapor pressure of molten zinc on the surface tension have been checked by making the measurements at atmospheric pressure and repeating at 1,800 Torr. The measurements were made on 99.999 pct zinc in the range from 436 to 806°C in an improved twin-tube MBP system. Results are that, over the given temperature range, the surface tension (γ) of zinc is given by γ (dynes/cm) = 839.7 − 125.7 e−0.00941(T−419.5) The temperature (T) is in degrees centigrade. A total of 130 experimental values were determined with a correlation index of 0.98 with the equation. Comparisons of this result with others in the literature are discussed.
TL;DR: In this paper, a Gaussian distribution of transition energies between localized and extended states is assumed for all four isomeric butenes near the critical region, including cis-butene-2 and isobutene.
Abstract: Electron mobilities are similar in all four isomeric butenes near the critical region, ∼ 10 cm2/V s at ∼420 K, and again in the low temperature liquids, ∼10−3 cm2/V s at ∼ 150 K, but not at intermediate temperatures. The Arrhenius temperature coefficient of the mobility decreases with increasing temperature in cis-butene-2 and isobutene, and increases with temperature in butene-1 and trans-butene-2. This difference in behavior is reflected in the temperature dependence of the dispersion parameter σ in the assumed Gaussian distribution of transition energies between localized and extended states. The extreme cases are trans-butene-2, for which dσ/dT = 0, and cis-butene-2, for which dσ/dT ≈ (2kCp)1/2. Mobilities in mixtures of cis- and trans-butene-2 do not display ideal solution behavior; the transition energies E0 go through a maximum. The mobility in liquid cis-butene-2 under its vapor pressure goes through a maximum value of 17 cm2/V s at 426 K, decreases to 14 cm2/V s at Tc = 433 K, then increases with...
TL;DR: The elastic surface wave device with a zero first-order temperature coefficient has been fabricated on Pyrex glass by use of a ZnO thin-film overlay as discussed by the authors, which was shown theoretically that the dispersion is very low at a znO film thickness of hK∼1.7.
Abstract: The elastic‐surface‐wave device with a zero first‐order temperature coefficient has been fabricated on Pyrex glass by use of a ZnO thin‐film overlay. The second‐order temperature coefficient of ZnO/Pyrex glass was about 1.24 times as much as that of ST‐cut quartz and was similar in sign. It is shown theoretically that the dispersion is very low at a ZnO film thickness of hK∼1.7, which gives a zero first‐order temperature coefficient.
TL;DR: In this article, the Boltzmann transport equation in the presence of a finite temperature gradient was considered for the case in which the single-particle energies are temperature dependent, and it was shown that possible additional effects arising from the spatial variation of the energies do not occur and that the transport coefficients are just those appropriate to the temperature of interest.
Abstract: The authors consider the Boltzmann transport equation in the presence of a finite temperature gradient for the case in which the single-particle energies are temperature dependent. It is shown that possible additional effects arising from the spatial variation of the energies do not occur and that the transport coefficients are just those appropriate to the temperature of interest. In particular, it is shown that the temperature coefficient of the band edge should appear in the expression for the absolute thermoelectric power of a semiconductor.
TL;DR: In this paper, a linearized equation deduced from the Mayadas-Shatzkes conduction model is proposed to achieve a more realistic fit to the variations in the temperature coefficient of resistance of polycrystalline films with thickness found experimentally.
Patent•
25 Aug 1977TL;DR: In this paper, a temperature compensation circuit comprising a transistor, a device (to which compensated voltage is to be applied) connected to the collector, and a plurality of resistors forming a voltage divider is described.
Abstract: Described is a temperature compensation circuit comprising a transistor, a device (to which compensated voltage is to be applied) connected to the collector, and a plurality of resistors forming a voltage divider. A node separates the resistors into two branches and is connected to the base, and a temperature sensor having a negative temperature coefficient of resistance is located in one of the branches. The branches are mutually adapted so that the ratio of the resistance of the branch containing the sensor to the sum of the resistances of both branches is a linear function of temperature. An application of this circuit to the control of the bias voltage supplied to an avalanche photodiode is specifically described.
TL;DR: The temperature coefficient of the Mossbauer recoil-free fraction is a useful guide to the nature of the lattice structure of tin compounds as discussed by the authors, and it can be used to estimate the temperature of the tin lattice.
Abstract: The temperature coefficient of the Mossbauer recoil-free fraction is a useful guide to the nature of the lattice structure of tin compounds.
TL;DR: In this paper, the semimetal-semiconductor transition in ytterbium has been studied in the pressure range 0.50 kbar and up to 600 degrees C using the Seebeck coefficient as a tool.
Abstract: The semimetal-semiconductor transition in ytterbium has been studied in the pressure range 0.50 kbar and up to 600 degrees C using the Seebeck coefficient as a tool. In the FCC phase the thermoelectric power exhibits a marked increase with pressure and the semimetal-semiconductor transition is observed as a change in the slope. In the semiconducting phase the thermopower initially increases very rapidly with pressure followed by a steep decrease at higher pressures. The temperature coefficient of thermopower in the semiconducting phase increase is large and positive in contrast to the semimetallic phase. The FCC-HCP transformation at high temperatures is reported. A semimetal-semiconductor transition in the HCP phase has also been observed. The experimental results are discussed qualitatively on the basis of a simplified two-band model.
Patent•
03 Aug 1977
TL;DR: In this paper, a porcelain dielectric material of BaTiO3, Bi2O3 - SnO2 ZrO2 - AlO3- SiO2- MnO system was obtained.
Abstract: PURPOSE:To obtain porcelain dielectric material of BaTiO3 - Bi2O3 - SnO2 ZrO2 - AlO3 - SiO2 - MnO system, having a high dielectric constant and a dielectric constant temperature coefficient below 1,800X10 / deg.C.