Electrical conductivity of pure and doped α-ferric oxides

Kim, Keu Hong; Lee, Sung Han; Choi, Jae Shi

doi:10.1016/0022-3697(85)90175-1

Cited by 25 publications

(7 citation statements)

References 25 publications

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“…Thus, gas-sensitivity is obtained through the gas-induced changes in the stoichiometry of the oxide. On the other hand, α-Fe 2 O 3 is a thermally stabile n-type semiconductor where the conductivity results from oxygen vacancies [16,34,35]; the reported band gap values are between 2.0 and 2.7 eV [36,37]. Oxides of this type, e.g.…”

Section: Characterizationmentioning

confidence: 96%

Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

2008

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Section: Characterizationmentioning

confidence: 96%

Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

2008

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“…Gardner et al [ 28 ] measured the oxygen deficit resulting from this equilibrium shift. Considering this structural disorder and the independence of the hematite conductivity regarding the oxygen partial pressure shown in the Figure 6 a, we can conclude that this material is an intrinsic semiconductor [ 27 , 29 ]. The large value of activation energy measured in this work ( Table 3 ) is the consequence of our experimental procedure where samples were sintered at 1300 °C and cooled under air laboratory.…”

Section: Resultsmentioning

confidence: 94%

“…Oxygen vacancies (

V_{O}^{• •}

) can be produced by heating this material following the disorder Equation (3) [27]:

O_{O}^{X} = \frac{1}{2} O_{2 false(g false)} + V_{O}^{• •} + 2 e'

…”

Section: Resultsmentioning

confidence: 99%

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Ba-Doped Iron Oxide as a New Material for NO2 Detection

2013

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Various compositions of barium-doped hematite between pure hematite (α-Fe2O3) and pure barium hexaferrite (BaFe12O19) were synthesized by solid state reaction. The XRD analyses confirmed the progressive evolution of the two crystalline phases. Tests as humidity sensors show that the electrical resistance of samples containing high proportions of hexaferrite phase is strongly influenced. Electrochemical impedance spectroscopy (EIS) analyses under air or argon revealed an intrinsic semiconducting behavior for hematite and samples doped with 3 and 4 wt % equivalent BaO. The samples containing higher proportions of barium exhibited an extrinsic semiconducting behavior characterized by a variation of the conductivity with the oxygen partial pressure. This study allowed us to define the percolation threshold of the barium hexaferrite crystalline phase in the hematite matrix. The value was estimated to hematite doped with 5 wt % BaO, i.e., 36 wt % of barium hexaferrite phase. EIS analyses under various NO2 partial pressures confirmed the sensitivity of these materials. The linearity of the response was particularly evident for the 5, 10 and 14 wt % samples.

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“…Specifically, Fe 2 O 3 is oxygen deficient and oxygen vacancies are considered as the predominant defect for the oxide. Oxygen vacancies are readily generated in the oxide when Fe 2 O 3 is heated at a low pressure [8,9]. Typically, oxygen vacancies in metal oxides act as adsorption sites for O 2 (g) because they serve as electron donors.…”

Section: Discussionmentioning

confidence: 99%

Kinetics of CO Oxidation over Unloaded and Pd-Loaded α-Fe2O3 Spherical Submicron Powder Catalysts: Photoacoustic Investigations at Low Pressure

et al. 2018

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In this study, α-Fe 2 O 3 spherical particles with an average diameter of approximately 200 nm were synthesized by a solvothermal method for use as both a catalyst and medium for a Pd catalyst. The kinetics of CO oxidation over powders of α-Fe 2 O 3 spherical particles and 14 wt % Pd/α-Fe 2 O 3 spherical particles were measured in a static reactor by using a CO 2 laser-based photoacoustic technique. The total pressure was fixed at 40 Torr for the CO/O 2 /N 2 mixture for temperatures in the range of 225-350 • C. The variation in the CO 2 photoacoustic signal with the CO 2 concentration during CO oxidation was recorded as a function of time, and the CO 2 photoacoustic data at the early reaction stage was used to estimate the rates of CO 2 formation. Based on plots of ln(rate) vs. 1/T, apparent activation energies were calculated as 13.4 kcal/mol for the α-Fe 2 O 3 submicron powder and 13.2 kcal/mol for the 14 wt % Pd/α-Fe 2 O 3 submicron powder. Reaction orders with respect to CO and O 2 were determined from the rates measured at various partial pressures of CO and O 2 at 350 • C. The zero-order of the reaction with respect to Po 2 was observed for CO oxidation over α-Fe 2 O 3 submicron powder, while 0.48 order to Po 2 was observed for CO oxidation over Pd/α-Fe 2 O 3 submicron powder. The partial orders with respect to P CO were determined as 0.58 and 0.54 for the α-Fe 2 O 3 , and the Pd/α-Fe 2 O 3 submicron powders, respectively. The kinetic results obtained from both catalysts were compared with those for the α-Fe 2 O 3 fine powder catalysts and were used to understand the reaction mechanism.

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Electrical conductivity of pure and doped α-ferric oxides

Cited by 25 publications

References 25 publications

Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

Ba-Doped Iron Oxide as a New Material for NO2 Detection

Kinetics of CO Oxidation over Unloaded and Pd-Loaded α-Fe2O3 Spherical Submicron Powder Catalysts: Photoacoustic Investigations at Low Pressure

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