Halbleitereigenschaften des Lanthankobaltit

Gerthsen, P.; Härdtl, Karl Heinz

doi:10.1515/zna-1962-0610

Cited by 46 publications

(13 citation statements)

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“…Finally, the parameter r of the optical theory can be calculated from the activation energy according to equation (8). Using the value q = 0.06 eV this parameter is found to be I' = 1.55, which is in good agreement with the result obtained from the above mentioned fit to the measured reflectivity curve.…”

Section: N-type P-fesisupporting

confidence: 77%

“…A recent review article by Appel [B] shows that the existence of small polarons has been established by electrical and optical experiments for few semiconductors only. One of the most carefully studied materials with small polaron conduction is LaCoO, [7, 8,9]. The results of this paper show that there is a remarkable similarity in the optical properties of P-FeSi, and LaCoO,.…”

Section: Introductionmentioning

confidence: 69%

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Optical Investigation of the Small Polaron in β‐FeSi₂

Birkholz¹,

Naegele²

1970

Physica Status Solidi (b)

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The reflectivity of or-FeSi, and also of (3-FeSi, doped with Co (n-type) or A1 (p-type) has been investigated for wavelengths between 1 and 25 pm. The results for or-FeSi, indicate metallic conduction in this material. The reflectivity of the undoped semiconducting phase P-FeSi, can be explained by a fundamental absorption corresponding to a band gap E , = = 0.8 eV and a reststrahlen band. The highest branch of the longitudinal optical phonons is found a t 20.6 pm. The reflectivity of p-FeSi, can be interpreted using Drude's theory of free carrier absorption. The optical properties of n-FeSi, cannot be explained by free carrier absorption. A consistent interpretation, however, is possible in terms of the small polaron picture. Using the experimcntal data of the dc conductivity and its activation energy the reflectivity of n-PeSi, can be calculated. There is good agreement with the observed values. These resuks confirm an analysis of the transport properties of fi-FeSi, which mas presented in a previous paper.Das ReflexionsverrnBgen von cr-FeSi, soivie von P-FeSi, mit Co-Dotierung (n-Typ) und Al-Dotierung (p-Typ) wurde im Wellenlangenbereich von 1 bis 25 pm untersucht. Die 1TeB-ergebnisse fur or-FeSi, stehen ini Einklang mit der metallischen Leitfahigkeit dieser Phase. Das Reflexionsvermogen der undotierten halbleitenden Phase P-FeSi, wird durch eine Grrindgitterabsorption entsprechend einem Bandabstand E, = 0,s eV und einer Reststrahlbande gedeutet. Der oberste Zweig der longitudinalen optischen Phononen liegt bei 20,6 pm. Das Reflexionsvermogen von p-FeSi, kann mittels der Drudeschen Theorie freier Ladangstrager erklart werdcn. Die optischen Eigenschaften von n-FeSi, konnen im Rahmen der Drudeschen Theorie nicht verstanden werden, lassen sich jedoch mittels der Theorie dcs kleinen Polarons beschreiben. Unter Verwendung der experimentellen Daten der Gleichst.romleitfahig1reit und ihrer Aktivierungsenergie 1a8t sich das Reflexionsvermogen von n-FeSi, berechnen. Die Ubcreinstimmung mit den beobachteten Werten ist gut. Durch dicse Ergebnisse wird eine friihere Analyse der Transporteigenschaften von P-FeSi, bestatigt.

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Section: N-type P-fesisupporting

confidence: 77%

Section: Introductionmentioning

confidence: 69%

Optical Investigation of the Small Polaron in β‐FeSi₂

Birkholz¹,

Naegele²

1970

Physica Status Solidi (b)

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“…A to hopping polaron model has been employed to explain conduction in the perovskite LaCoO3 [56]. decrease in the probability of hopping of the charge carriers would be expected to accompany these changes in the bonding .…”

Section: S ) It Is Unlikely That Processesmentioning

confidence: 99%

Electrical Transport in Rare Earth Ortho-Chromites, -Manganites and -Ferrites

Rao

Wanklyn

Rao

1995

Solid State Chemistry

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Rare earth ortho-chromites, -manganites and -ferrites are p-type semiconductors with conductivities in the range 10-4-10-' ohm-' cm-'. The conductivity in each series of perovskites decreases with the increasing atomic number of the rare earth. The ionic contribution to conductivity is small in all the three series of solids. None of these solids exhibits intrinsic behavior up to --1000°C. The conductivity behaviors of these rare earth compounds reflect the known crystallographic, dielectric and magnetic transitions in these materials. Seebeck coefficients in these compounds are large, typical of narrow-band materials; the Seebeck coefficients show marked changes at temperatures where magnetic and dielectric transitions occur. The electrical transport properties of all the three series of rare earth compounds are essentially controlled by the d-electrons of the transition elements which show localized behavior. This conclusion is in agreement with the results from optical spectra and the predictions of Goodenough. In all these compounds small polarons seem to be responsible for the conduction.

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“…B-site substitution of Co with Fe improves the chemical stability of the perovskite towards reducing atmospheres, while simultaneously decreasing the electronic conductivity [1,2]. Depending on the cation composition as well as T-and pO 2 -range, the electronic conductivity was either reported to be thermally activated or to exhibit a metallic conduction mechanism [1,[3][4][5][6][7]. However, the σ-vs. pO 2 -and σ-vs. T-dependences, which are frequently used for analysis of defect chemistry and conduction mechanism of LSCF, have the drawback of being superimposed by the variations of δ with pO 2 and T. As previously reported, the increase in oxygen deficit with increasing temperature and decreasing pO 2 , which is on the one hand desirable to enhance oxygen exchange with the gas phase and oxygen transport through the bulk of the solid, can on the other hand have a deteriorating effect on electronic transport [3,[8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%