NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Cation Ordering types and Dielectric Properties in the Complex Perovskite Ca(Ca1/3Nb2/3)Od3^
Published
Author(s)
Igor Levin, Julia Y. Chan, Richard G. Geyer, James E. Maslar, Terrell A. Vanderah
Abstract
In the present work the effects of cation ordering on dielectric properties were isolated by investigating three polymorphs of Ca(Ca1/3Nb2/3)O3 that feature different arrangements of the Ca2+ and Nb5+ 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(111)c ordering. Rietveld refinements of structural models for the three Ca4Nb2O9 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-b-b+ 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 Nb5+. 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(111)Lc 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.
Levin, I.
, Chan, J.
, Geyer, R.
, Maslar, J.
and Vanderah, T.
(2001),
Cation Ordering types and Dielectric Properties in the Complex Perovskite Ca(Ca<sub>1/3</sub>Nb<sub>2/3)O</sub>d3^, Journal of Solid State Chemistry
(Accessed October 8, 2025)