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January 27th, 2010

Doping and Atomic Site Substitution in the Dielectric Ceramics Ti(Al)O2 Rutile and (1−x)Ca2/5Sm2/5TiO3–xLi1/2Sm1/2TiO3 Perovskite

Published on January 27th, 2010 | By: pwray@ceramics.org

Volume 93 Issue 1, Pages 251 – 255


Toru Yamashita, John Barry, Richard Taylor
Published Online: Nov 11
2009 2:33PM

DOI: 10.1111/j.1551-2916.2009.03318.x




Temperature-stable, high-permittivity (high-dielectric
constant) ceramics are used as resonators for microwave
telecommunications. Research and development in this area is aimed at
increasing the dielectric constant (in order to reduce component size)
while maintaining very high quality factor (low dielectric loss). This
present work is a synchrotron X-ray powder diffraction study of high
quality factor, high permittivity ceramics of the Ti(Al)O2
and (1−x)Ca2/5Sm2/5TiO3xLi1/2Sm1/2TiO3
families. The synchrotron powder diffraction was used to investigate
doping of Al onto the Ti site in Ti(Al)O2. It
was found that the lattice parameters in Ti(Al)O2
are not affected by the Al doping. Although this null result does not
give any evidence for substitution of Al on the Ti site, it does not
exclude the possibility that a small proportion of the Al ions do
substitute for Ti in Ti(Al)O2. In (1−x)Ca2/5Sm2/5TiO3xLi1/2Sm1/2TiO3
the variation of lattice parameters and crystal structure versus x, and the possibility of substitution of Li onto the
Ti site were investigated. Single phase samples with the orthorhombic
CaTiO3 perovskite structure were obtained for
0.20<x<0.50. It was found that the unit
cell volume increased in an inverse linear relationship with the
(decreasing) vacancy concentration. Rietveld analysis of the powder
diffraction data shows that there is no substitution of Li on the Ti
site in (1−x)Ca2/5Sm2/5TiO3xLi1/2Sm1/2TiO3.


Online Access to Journal of the American Ceramic Society

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