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Title: Cation Ordering Types and Dielectric Properties in the Complex Perovskite Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3}

Abstract

In the present work the effects of cation ordering on dielectric properties were isolated by investigating three polymorphs of Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3} that feature different arrangements of the Ca{sup 2+} and Nb{sup 5+} cations on the B-sites of the perovskite structure. Dielectric measurements at frequencies above 1 GHz revealed a systematic dependence of the properties on the type of cation ordering. In particular, the structure with 2:1 ordering exhibited a lower dielectric constant and a significantly more negative temperature coefficient of resonance frequency than the structures with 1:1 and newly described k=1/4[1 1 1]*{sub c} ordering. Rietveld refinements of structural models for the three Ca{sub 4}Nb{sub 2}O{sub 9} polymorphs were conducted using X-ray and neutron powder diffraction data to elucidate structural details that could be correlated with the changes in dielectric properties. In all three polymorphs the cation ordering was combined with the same b{sup {minus}}b{sup {minus}}c{sup +} octahedral tilt system, and the structural refinements yielded similar magnitudes of the tilting angles. The most significant crystal-chemical difference between the three polymorphs was in the coordination environment of Nb{sup 5+}. Analysis of the refined bond distances indicated increasing average distortion of the Nb nearest-neighbor environment in going from the 1:1more » to the k=1/4[1 1 1]*{sub c} to the 2:1 ordered structure. The increased fraction of strongly compressed Nb-O bonds in the 2:1 structure associated with the large distortion was correlated with the decrease in dielectric constant and more negative value of temperature coefficient of the resonant frequency obtained for this polymorph. Raman spectra obtained for the three polymorphs exhibited differences that were consistent with the observed structural chemistry.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Institute of Standards and Technology, Materials Science and Engineering Laboratory, Gaithersburg, Maryland (US); Electronics and Electrical Engineering Laboratory, Boulder, Colorado (US); Chemical Science and Technology Laboratory, Gaithersburg, Maryland (US)
Sponsoring Org.:
None (US)
OSTI Identifier:
784335
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 156; Journal Issue: 1; Other Information: PBD: 1 Jan 2001; Journal ID: ISSN 0022-4596
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CATIONS; CHEMISTRY; DIELECTRIC MATERIALS; DIELECTRIC PROPERTIES; DIFFRACTION; NEUTRONS; PEROVSKITE; RAMAN SPECTRA; RESONANCE; STRUCTURAL MODELS; TEMPERATURE COEFFICIENT; CALCIUM OXIDES; NIOBIUM OXIDES; PEROVSKITES; CALCIUM IONS; NIOBIUM IONS; SPATIAL DISTRIBUTION; X-RAY DIFFRACTION; NEUTRON DIFFRACTION; GHZ RANGE; TEMPERATURE DEPENDENCE; BOND LENGTHS; STRUCTURAL CHEMICAL ANALYSIS; EXPERIMENTAL DATA

Citation Formats

Levin, I, Chan, J Y, Geyer, R G, Maslar, J E, and Vanderah, T A. Cation Ordering Types and Dielectric Properties in the Complex Perovskite Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3}. United States: N. p., 2001. Web. doi:10.1006/jssc.2000.8971.
Levin, I, Chan, J Y, Geyer, R G, Maslar, J E, & Vanderah, T A. Cation Ordering Types and Dielectric Properties in the Complex Perovskite Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3}. United States. doi:10.1006/jssc.2000.8971.
Levin, I, Chan, J Y, Geyer, R G, Maslar, J E, and Vanderah, T A. Mon . "Cation Ordering Types and Dielectric Properties in the Complex Perovskite Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3}". United States. doi:10.1006/jssc.2000.8971.
@article{osti_784335,
title = {Cation Ordering Types and Dielectric Properties in the Complex Perovskite Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3}},
author = {Levin, I and Chan, J Y and Geyer, R G and Maslar, J E and Vanderah, T A},
abstractNote = {In the present work the effects of cation ordering on dielectric properties were isolated by investigating three polymorphs of Ca(Ca{sub 1/3}Nb{sub 2/3})O{sub 3} that feature different arrangements of the Ca{sup 2+} and Nb{sup 5+} cations on the B-sites of the perovskite structure. Dielectric measurements at frequencies above 1 GHz revealed a systematic dependence of the properties on the type of cation ordering. In particular, the structure with 2:1 ordering exhibited a lower dielectric constant and a significantly more negative temperature coefficient of resonance frequency than the structures with 1:1 and newly described k=1/4[1 1 1]*{sub c} ordering. Rietveld refinements of structural models for the three Ca{sub 4}Nb{sub 2}O{sub 9} polymorphs were conducted using X-ray and neutron powder diffraction data to elucidate structural details that could be correlated with the changes in dielectric properties. In all three polymorphs the cation ordering was combined with the same b{sup {minus}}b{sup {minus}}c{sup +} octahedral tilt system, and the structural refinements yielded similar magnitudes of the tilting angles. The most significant crystal-chemical difference between the three polymorphs was in the coordination environment of Nb{sup 5+}. Analysis of the refined bond distances indicated increasing average distortion of the Nb nearest-neighbor environment in going from the 1:1 to the k=1/4[1 1 1]*{sub c} to the 2:1 ordered structure. The increased fraction of strongly compressed Nb-O bonds in the 2:1 structure associated with the large distortion was correlated with the decrease in dielectric constant and more negative value of temperature coefficient of the resonant frequency obtained for this polymorph. Raman spectra obtained for the three polymorphs exhibited differences that were consistent with the observed structural chemistry.},
doi = {10.1006/jssc.2000.8971},
journal = {Journal of Solid State Chemistry},
issn = {0022-4596},
number = 1,
volume = 156,
place = {United States},
year = {2001},
month = {1}
}