Proceedings of the Eighth Meeting of the International Committee of Electrochemical Thermodynamics and Kinetics

DC and ac electrical conductivities of silicon dioxide thermally grown on p‐ (boron‐doped) and n‐type (phosphorous‐doped) silicon have been measured in the temperature range of 25°–1100°C. Total dc conductivities varied from 10−9 to 10−16 Ω−1cm−1 in the temperature range of 25°–960°C. Arrhenius plots for total dc conductivities of SiO2 grown on both the substrates exhibit two regions. Below 450°C, the conductivities were independent of temperature and are suggested to be governed by impurities. Above 450°C, the total dc conductivities increased with increase in temperature. The activation energies of conduction in the temperature range 500°–960°C were estimated to be 1.65 and 2.10 eV for SiO2 grown on p‐ and n‐type silicon, respectively. DC polarization measurements carried out in this temperature range suggest that conduction in SiO2 is ionic as well as electronic. The ionic conduction is believed predominantly to be due to the transport of oxygen ions. AC conductivities were also measured in the temperature range of 550°–1100°C. The activation energies for the conduction in this temperature range were estimated to be 1.55 eV for SiO2 on p‐type silicon and 1.86 eV for SiO2 on n‐type silicon. These values are in close agreement with the values reported in the literature. AC conductivity of SiO2 grown on n‐type silicon was found to be lower than that of SiO2 grown on p‐type silicon.

Section: Isilsio21silmmentioning

confidence: 99%

Electrical Conductivity of Silicon Dioxide Thermally Grown on Silicon

Srivastava

Prasad

Wagner

1985

“…The Hebb-Wagner d-c polarization experiment (19) was adopted for the present study of ~-PbF2. Consider A reversible electrode consisting of a more noble metal (Me) coexisting with its fluoride (MeF~) provides a fixed and known PF2 on one side of the cell.…”

Section: D-c Polarization Studymentioning

confidence: 99%

“…If the right-hand reversible electrode is made negative, under the steady-state condition the ionic current is blocked and the steadystate polarization current i® is then carried exclusively by electrons and electron holes according to the equation RT L --ie + ie = F'--'~ {Co° [exp (u) - -1] +~e ° [1--exp(--u)]) [1] where L is the cell constant (thickness/area), co° and ao ° are, respectively, the partial electron hole and electronic conductivities at the equilibrium fluorine activity of the reversible electrode and u --EF/RT, where E is the applied voltage, F is Faraday's constant, and R and T have their usual meaning. The details of the theory have been given elsewhere (19)(20)(21).…”

Section: D-c Polarization Studymentioning

confidence: 99%

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The Electrical Conductivity of β ‐ PbF2

Fang¹,

Rapp²

1978

The electrolytic properties of pure/~-PbF~ were studied by a-c conductivity measurements and Hebb-Wagner d-c polarization experiments as a function of fluorine pressure and temperature. The partial ionic and electronic conductivities of ~-PbF2 were determined over a range of fluorine pressure and temperature. Because of the introduction of p-type electronic conduction, the electrolytic domain of ~-PbF~ is truncated at high values of PF2, with PF~ = 10 -~1 arm at 492°C. At low PF2, predominant ionic conduction extends to PF2 for the coexistence of Pb and PbF2.The electrolytic properties of nominally pure and doped p-PbF~ and ~-PbF2 have been extensively investigated recently (1-16). Bonne and Schoonman (13) calculated the temperature dependences of the concentrations and mobilities of the interstitial fluoride ions and anion vacancies based on their a-c conductivity measurements of pure and doped p-PbF2 and existing literature data. Their results indicated that interstitial fluoride ions are the principal mobile species in pure ~-PbF2 for temperatures greater than 300°C. Hebb-Wagner polarization experiments have also been conducted by many authors to elucidate the electronic conductivity in PbFe. Kennedy et al. (4) reported that the electronic conductivity of pure ~-PbF~ at 150°C was p-type. At 25°C Kennedy and Miles (12) could not specify whether the electronic current in fl-PbF2 was carried by electrons or 'holes. Benz (10) found that pure ~-PbF~ was essentially an n-type conductor from 400 ° to 600°C. Schoonman et al. (8) also found an n-type conductor for pure ~-PbF2 single crystal from 52 ° to 137°C. Joshi and Liang (9) reported that ~-PbFe is a p-type conductor.Both ~-PbF2 and ~-PbF2 are known to be predominant ionic conductors. To elucidate the ionic domain (17, 18) of PbF2, the determination of the range of log PF2 beyond which electronic conduction becomes appreciable is studied here. Previous studies did not include several well-defined fluorine activities in conductivity studies on PbF2. The present study consists of measurements of the total a-c conductivity, together with the measurements of the partial conductivity for electrons and electron holes as a function of fluorine activity. These results define the limits for the electrolytic domain for PbFe. Hebb-Wagner polarization studies of ~-PbF2 also clarify the controversial results regarding n-type conduction as the predominant electronic conduction mode.

“…The charge carrier distribution is one of the essential aspects for understanding the application mechanism of mixed ionic-electronic conductors ͑MIECs͒. There have been a number of theoretical treatments of this topic, such as Wagner's fundamental work 1,2 on mixed conduction in general, and some others on fuel cell application in particular. [3][4][5][6][7][8] The essential problem for analytically modeling mixed conduction is how to decouple ionic and electronic transports.…”

mentioning

confidence: 99%

Comparison of the Mobile Charge Distribution Models in Mixed Ionic-Electronic Conductors

Chen

2004

Different models of the steady-state ionic and electronic defect distributions in mixed ionic-electronic conductors under chemical and electrical potential gradients are compared in this paper. Simple analytical expressions without any dummy parameters are obtained under the local charge neutrality approximation and constant electrical field approximations, respectively. The accuracies of the approximate solutions are evaluated by numerically solving the Nernst-Plank-Poisson equation set using the Galerkinweighted residual finite element method. The numerical results show that the constant electrical field approximation introduces errors of less than 10% so long as the average ionic transference number is not smaller than 0.5; and that the local charge neutrality approximation introduces only very small errors ͑less than 3%͒ even when the average ionic transference number is as small as 0.001. Analytical criteria for the constant electrical field approximations to be valid are also given, and the effects of dopant concentration and the sample thickness are discussed. The analytical criteria are in agreement with the numerical results.