Cart (Loading....) | Create Account
Close category search window

Polarizing-field orientation and thermal treatment effects on the dielectric behavior of fluorapatite

Sign In

Cookies must be enabled to login.After enabling cookies , please use refresh or reload or ctrl+f5 on the browser for the login options.

Formats Non-Member Member
$31 $31
Learn how you can qualify for the best price for this item!
Become an IEEE Member or Subscribe to
IEEE Xplore for exclusive pricing!
close button

puzzle piece

IEEE membership options for an individual and IEEE Xplore subscriptions for an organization offer the most affordable access to essential journal articles, conference papers, standards, eBooks, and eLearning courses.

Learn more about:

IEEE membership

IEEE Xplore subscriptions

4 Author(s)
Vassilikou-Dova, Aglaia ; Department of Physics, Solid State Physics Section, University of Athens, Panepistimiopolis, 157 84 Zografos, Greece ; Kalogeras, Ioannis M. ; Macalik, Bogusaw ; Londos, Charalambos A.

Your organization might have access to this article on the publisher's site. To check, click on this link: 

A thermally stimulated depolarization currents (TSDC) study in natural fluorapatite single crystals has established different relaxation mechanisms for two polarization orientations (Ep parallel and perpendicular to the crystallographic c axis), which are discussed in relation to the defect chemistry and the specific columnar structure in apatite. The intensities of the thermostimulated current signals between the two poling field orientations demonstrate a difference of at least one order of magnitude, with the higher one recorded for the electric field parallel to the c axis. The TSDC thermogram appearing with the electric field parallel to c axis, in the 10–320 K range, consists of a broad and complex band (HT), with a maximum around 300 K. The relative intensity of associated current signals is indicative of extensive dipole-like ionic motions along c axis with a distribution in their activation energies ranging between 0.14 and 0.85 eV. The microdomain structure of fluorapatite along c axis permits the formation of charge layers at the interfaces. After annealing, the induced changes of size and/or shape of the interfaces could explain the observed changes of band intensity and location. With the electric field perpendicular to c axis, the spectrum consists of at least five well-defined relaxation bands, the high temperature ones (HT1, HT2, HT3) decreasing after heating at 673–873 K. The most dramatic change was recorded for an intermediate LT2 single-relaxation band located around 185 K, with a high activation energy of 1.06 eV, which manifested a significant growth after annealing. Rietvelt analysis of the x-ray diffraction patterns of the original and annealed apatite powders, indicates- change in the unit cell parameters of the hexagonal structure (i.e., a increases from 9.3921 to 9.3940 Å after annealing), which can be related to the establishment of a new equilibrium distribution of the abundant trivalent rare-earth (Ce, La, Nd, Pr,…) impurity ions. The origin of the TSDC bands is discussed and tentative correlations are suggested, in terms of substitute aliovalent ions-vacancy dipoles. The thermal response of the high temperature relaxation bands in the case of Ep⊥c axis, is characteristic of dipole clustering phenomena—although an explanation based on localized changes in the structural environment of the pertinent dipoles/ions cannot be disregarded. © 1999 American Institute of Physics.

Published in:

Journal of Applied Physics  (Volume:85 ,  Issue: 1 )

Date of Publication:

Jan 1999

Need Help?

IEEE Advancing Technology for Humanity About IEEE Xplore | Contact | Help | Terms of Use | Nondiscrimination Policy | Site Map | Privacy & Opting Out of Cookies

A not-for-profit organization, IEEE is the world's largest professional association for the advancement of technology.
© Copyright 2014 IEEE - All rights reserved. Use of this web site signifies your agreement to the terms and conditions.