Electrical conductivity and defect structure of polycrystalline tin dioxide doped with antimony oxide

Electrical conductivity () of tin dioxide doped with antimony has been measured as functions of temperature and oxygen partial pressure (p0_2> ). Variation of electrical conductivity is explained by assuming that the antimony oxide forms a substitutional solid solution and doubly ionized oxygen vacancies are predominant defects. Above –10^–5 atm oxygen partial pressure antimony ions are present predominantly in the pentavalent state in tin dioxide lattice. However, it is converted to the trivalent state below this oxygen partial pressure accompanied by a sudden rise in conductivity.     

Electrical conductivity of polycrystalline semiconductors

A phenomenological model for the electrical conductivity in polycrystalline semiconductors is presented, using the assumption that an isotype heterojunction with a certain interface state density exists at the grain-intergrain domain interface. Tunnelling, thermionic emission of carriers through the intergrain barriers and ohmic conductivity of the heterojunction are all considered as possible charge transfer mechanisms. Explicit calculations are performed for wide-gap n-type semiconductors and a general expression is derived for the electrical conductivity. It is shown that the known models of Petritz and van den Broek, and also the expression for the conductivity of monocrystalline semiconductors, are special limiting cases of the theory presented.     

Electrical conductivity of polycrystalline lithium vanadium bronzes

Polycrystalline lithium vanadium bronzes, Li _x V₂O ₅ with different values of x have been prepared by both high temperature synthesis and room temperature chemical lithiation techniques. Electrical conductivity of the specimens initially increases with lithium concentration. The maximum conductivity is obtained in the phase for the high temperature prepared specimens and in Phase II for the room temperature prepared specimens. V⁴⁺ concentration of the specimens has been measured by a spectrophotometric technique and its variation has been correlated with the preparation condition and conductivity.     

Electrical conductivity of single crystal and polycrystalline yttria-stabilized zirconia

The conductivity of several single crystal and polycrystalline Y₂O₃-ZrO₂ samples has been studied by complex impedance and four-probe direct current techniques. For single crystals only one arc, due to lattice conductivity, was observed in the complex impedance representation. Polycrystalline materials showed a second arc, due to grain boundary resistance, the extent of which decreased as the impurity concentration was reduced and as the electrolyte microstructure improved. The activation energies for the volume and total conductivity of the purest polycrystalline samples were similar and agreed with those for the single crystals. These values, however, decreased by 20 to 25 kJ mol^–1 on going from low (<550° C) to high (>850° C) temperatures. The change in the activation energy with temperature is thought to be due to a gradual transition between an association region, where vacancies are bound to dopant cations, and a dissociation region where vacancies are free and mobile.     

Electrical properties of high purity tin dioxide doped with antimony

The electrical conductivity of high purity tin dioxide doped with antimony was studied at temperatures of 900 to 1200° C and partial pressures of oxygen between 10^–8 and 1 atm. For specimens having a dopant concentration over 1 × 10¹⁹Sb cm^–3, the electrical conductivity decreased slightly with temperature and independent of oxygen partial pressure. The electrical conductivity of specimens having a dopant concentration under 1 × 10^–8Sb cm^–3 increased with temperature and with decreasing partial pressure of oxygen. The significance of the dopant and the thermally created defects is discussed.     

Diffusivity and thermal conductivity in solid and liquid tin

A method for determination of diffusivity of liquid metals in a hemispherical volume is described and experimental results are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 3, pp. 490–494, September, 1973.     

Electrical resistivity and deviation from matthiessen's rule in polycrystalline lead-doped tin

The results of measurements of the electrical resistivity, of lead-doped (weight concentrations: 0.001, 0.01, 0.1, and 1%) polycrystalline tin are presented. The experiments were performed using a comparative method with the aid of a tantalum thermomagnetic modulator applied as a null indicator. A nonlinear dependence of the residual resistivity on lead concentration was obtained. An anomalous character ofp(T) dependence was observed in the lowest-Pb concentration sample (0.001%). The deviation of the resistivity-temperature characteristics from Matthiessen's rule (DMR) was determined. The characteristics of the DMR do not show humps in the temperature range from 3.7 to 28 K.     

Morphology of polycrystalline ZnO and its physical properties

Five commercial polycrystalline ZnO samples with different morphologies (nodular and needle-like) have been studied. Nodular ZnO crystallites reveal lower polydispersity, higher ultraviolet luminescence (380 nm), low green luminescence (500 nm), a small ESR signal with g=1.96 and a density close to the theoretical value for ZnO with the wurtzite structure. Needle-like ZnO crystallites have a higher polydispersity, higher green luminescence, higher ESR signal with g=1.96 and lower values of density. The observed differences in the physical properties are associated with the presence of oxygen vacancies in needle-like particles and probably also interstitial zinc atoms in nodular particles.     

Electrical and optical properties of transparent conducting tin doped ZnO thin films

Electrical, optical and structural properties of tin doped ZnO thin films were investigated for various tin (Sn) doping concentrations. Sol gel method was used to deposit the films on microscopic glass slides and silicon substrate. UV–Visible spectrometer analysis showed excellent optically transparent oscillating natures with transparency above 85% in the visible range. Band gap of 3.24 eV was deduced for Sn doping concentration of 4 at% using envelope method. Scanning electron microscopy (SEM) was employed to study the morphology of the films. Crystallinity of the film was investigated by X-Ray diffraction (XRD), which revealed polycrystalline nature with orientation towards c-axis. Resistivity of 3.11 Ω-cm with minimum stress value of 8.11 × 10⁻³ MPa was measured for Sn doping concentration of 4 at%.     

Electrical conductivity in non-stoichiometric titanium dioxide at elevated temperatures

The electrical conductivity of polycrystalline titanium dioxide prepared by a liquid mix technique was measured for the oxygen partial pressure range of 10° to 10^–19 atm and temperature range of 850 to 1050° C. The data were found to be proportional to the –1/6 power of oxygen partial pressure for the oxygen pressure range 10^–19 to 10^–15 atm, and proportional to for the oxygen pressure range >10^–15 atm. The region of linearity where the electrical conductivity varied as the –1/4 power of increased as the temperature was decreased. There was evidence of p-type behaviour for 10^{ - 2}$$ " align="middle" border="0"> atm in the temperature range 950 to 850° C, although the measured data were insufficient to assign a pressure dependence. Electrical conductivity minima in the log against log plot moved to lower as the temperature was decreased in the range 950 to 850° C. The measured oxygen pressure dependence of electrical conductivity in the lowest region supports the oxygen vacancy defect model. The observed data are consistent with the presence of very small amounts of acceptor impurities. A binding energy of 0.67 eV between the acceptor impurity and its compensating oxygen vacancy was also determined.     

The density and thermal conductivity of solid nitrogen and carbon dioxide

The density and thermal conductivity of solid nitrogen and carbon dioxide have been measured. The solids were condensed from the gas phase under cryopumping conditions over a wide range of deposition rates and temperatures. The density and thermal conductivity of solid nitrogen increased with increasing deposition rate and temperature but carbon dioxide showed different behaviour. At a deposition rate of 400 mg s^?1 m^?2 and a temperature of 108 K the density and thermal conductivity fell sharply, the density reaching a value which was only 20% of that of the bulk crystals.     

The effect of Sb and Nb on the electrical conductivity of tin dioxide based ceramics

The electrical conductivity of Mn doped SnO₂ systems prepared by an organic route (Pechini’s method) has been investigated as a function of antimony and niobium concentration. The conductivity increases with the increase of both concentration ions, however, in a different manner. While the conductivity of niobium doped ceramics increases with the power of 1.6 for the entire range of concentrations studied (0.01–0.7 mol%), the conductivity of antimony doped ceramics increases with the power of 1.9 in the range 0.01–0.05 mol% of Sb; 3.7 in the range 0.05–0.30 mol% and 1.8 in the range 0.30–0.70 mol%. This behavior is attributed to the existence of two stable oxidation states for antimony: Sb³⁺ and Sb⁵⁺, while for niobium there is only one: Nb⁵⁺. The power of 3.7 for Sb would be related to the segregation of this ion on the grain boundary accompanied by an additional contribution coming from the substitution of Sn²⁺ by Sb³⁺ on the grain surface.     

Alternating current conductivity of solid and liquid phases in the tin diiodide-silver diiodide system

Electrical conductivity was measured in the solid and molten Snl₂-Agl system between 70 and 85 mol% Agl. High conductivity and a broad region of solid solubility, placed between 80 mol%, 75 mol% and about 40 mol% Agl and 635.8, 380 and 559.8 K, respectively, was confirmed. The addition of the Snl₂ to the molten Agl is accompanied by a decrease in the electrical conductivity and an increase in the activation energy. Temperature dependences of the specific conductivity indicate a similarity between molten mixtures and solid superionic phases.     

Electrical properties of polycrystalline ZnO : Cu obtained from freeze-dried ZnO+copper(II) acetate powders

Highly homogeneous mixtures of powders containing ZnO and monohydrated copper(II) acetate, (CH₃COO)₂CuH₂O, AcCuH₂O were obtained by freeze drying. Thermal analysis and high-temperature X-ray diffraction showed that pure freeze-dried AcCuH₂O powder decomposed to CuO, in air, at temperatures above 325 °C. Due to the polymeric nature of AcCuH₂O, the powder mixtures were compacted without pressing additives. Pellets with ZnO+x mol % Cu (x=0.05, 0.5, and 5.0) compositions were sintered in air from 750 to 1150 °C for 1 h. After sintering, the density, shrinkage and mass loss increased as the concentration of AcCuH₂O increased. A microstructural analysis of samples sintered at 950 °C for 1 h revealed Cu-doped ZnO grains with Cu-clusters of x=5.0 mol % Cu; the J–E curves showed that both the breakdown electric field, E_br, and the nonlinearity coefficient, , increased as x increased from 0.05 to 0.5. Complex acceptor defects involving Cu⁺ _Zn in the grain boundary are believed to have compensated for the n-type conductivity of the ZnO grains, giving rise to high E_br values.     

Size effects of polycrystalline tin films

The electrical properties of polycrystalline tin films evaporated onto a cooled quartz substrate were examined in situ and in vacuum. The relationship between internal size effect and annealing temperature was considered. It was found that the parameter * of grain-boundary scattering decreased as the annealing temperature was increased.