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Title: Cathodoluminescence from Mixed KTaO3-KNbO3 Crystals

Abstract

Cathodoluminescence spectra are shown for a sequence of mixed crystals of KTaO{sub 3}:KNbO{sub 3}. The luminescence emission bands are broadly similar across the spectrum from 250 to 850 nm, although their relative strengths are sensitive to composition and temperature. A UV band near 330 nm is only well resolved in some compositions and a broad line near 700 nm may arise from Cr ions. The presence of low temperature phase transitions within the crystals is evidenced by intensity steps and spectral changes of the cathodoluminescence. Hysteresis is seen, as are domain effects and electric field shifts of the transition temperatures. The cathodoluminescence of the surface material reveals more transitions than are reported from earlier bulk studies.

Authors:
 [1];  [2];  [3];  [1];  [4]
  1. University of Sussex, Brighton, UK
  2. University of Sussex, Brighton, UK, Ege University, Izmir, Turkey
  3. University of Sussex, Brighton, UK, Beijing Normal University, Beijing, China
  4. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
979580
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physica Status Solidi C; Journal Volume: 4; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CATHODOLUMINESCENCE; POTASSIUM OXIDES; TANTALUM OXIDES; NIOBIUM OXIDES; SPECTRA; PHASE TRANSFORMATIONS

Citation Formats

Nunn, P. J. T., Kibar, R., Wang, Y., Townsend, P. D., and Boatner, Lynn A. Cathodoluminescence from Mixed KTaO3-KNbO3 Crystals. United States: N. p., 2007. Web.
Nunn, P. J. T., Kibar, R., Wang, Y., Townsend, P. D., & Boatner, Lynn A. Cathodoluminescence from Mixed KTaO3-KNbO3 Crystals. United States.
Nunn, P. J. T., Kibar, R., Wang, Y., Townsend, P. D., and Boatner, Lynn A. Mon . "Cathodoluminescence from Mixed KTaO3-KNbO3 Crystals". United States. doi:.
@article{osti_979580,
title = {Cathodoluminescence from Mixed KTaO3-KNbO3 Crystals},
author = {Nunn, P. J. T. and Kibar, R. and Wang, Y. and Townsend, P. D. and Boatner, Lynn A},
abstractNote = {Cathodoluminescence spectra are shown for a sequence of mixed crystals of KTaO{sub 3}:KNbO{sub 3}. The luminescence emission bands are broadly similar across the spectrum from 250 to 850 nm, although their relative strengths are sensitive to composition and temperature. A UV band near 330 nm is only well resolved in some compositions and a broad line near 700 nm may arise from Cr ions. The presence of low temperature phase transitions within the crystals is evidenced by intensity steps and spectral changes of the cathodoluminescence. Hysteresis is seen, as are domain effects and electric field shifts of the transition temperatures. The cathodoluminescence of the surface material reveals more transitions than are reported from earlier bulk studies.},
doi = {},
journal = {Physica Status Solidi C},
number = 3,
volume = 4,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • No abstract prepared.
  • Semiconducting KTaO3 single crystals have been investigated as a model potential photoanode for hydrogen production using photoelectrochemical (PEC) cells. In order to modify the electronic properties of KTaO3 by reducing the bandgap and thereby increase the absorption of light at longer wavelengths, KTaO3 single crystals were doped during the crystal growth process. A wide range of dopant elements was employed that consisted primarily of transition metals - due to the established effects they have exhibited in modifying the properties of other semiconducting systems such as TiO2. With the exception of the crystals grown with LiCO3 or B2O3 added to themore » melt (resulting in crystals that were not effectively doped), the crystals exhibited n-type behavior with carrier concentrations ranging from 4 x 1018 to 2.6 x 1020 cm-3. The position of the band edges indicated that the crystals were thermodynamically capable of water dissociation without the application of an external bias. External quantum yield (QY) measurements revealed that the samples were photoactive up to a wavelength of ~350 nm. Higher QY s were measured when some of the crystals were thermochemically treated in a CO atmosphere. The indirect bandgap and a parameter denoted as E1 that is related to the direct band edge of the semiconductor were found to be the same within the statistical error for all the samples. These results indicate that the various dopants and treatments did not produce changes in the KTaO3 electronic structure that were sufficient to significantly modify the behavior exhibited by this material in a PEC cell.« less
  • Cathodoluminescence (CL) emission from as-grown, thermochemically reduced and mechanically damaged LiNbO/sub 3/ single crystals has been studied in the scanning electron microscope. Three emission bands at 410, 525, and 580 nm have been observed. The CL spectra strongly depend on the deformation at the surface region. An intense emission with its peak in the infrared region has been observed. Severe damage is induced by irradiation with the electron microscope beam at very high current intensities.