CHANGES IN THE CRYSTAL-STRUCTURE AND DIELECTRIC PROPERITES OF THE COMPLEX PEROVSKITE SR(GA0.5TA0.5)O-3 WITH A-SITE CATION SUBSTITUTION

Citation
T. Fujii et al., CHANGES IN THE CRYSTAL-STRUCTURE AND DIELECTRIC PROPERITES OF THE COMPLEX PEROVSKITE SR(GA0.5TA0.5)O-3 WITH A-SITE CATION SUBSTITUTION, Nippon Seramikkusu Kyokai gakujutsu ronbunshi, 106(7), 1998, pp. 669-675
Citations number
13
Language
GIAPPONESE
art.tipo
Article
Categorie Soggetti
Material Science, Ceramics
ISSN journal
0914-5400
Volume
106
Issue
7
Year of publication
1998
Pages
669 - 675
Database
ISI
SICI code
0914-5400(1998)106:7<669:CITCAD>2.0.ZU;2-J
Abstract
A-site cation substitution with Ba2+ or Ca2+ ions was made for the com plex perovskite Sr(Ga0.5Ta0.5)O-3 phase to modify its dielectric prope rties. The largely sized Ba2+ ions could be incorporated in the A-site sublattice up to 55 mol% without cation ordering. On the contrary, th e A-site Sr2+ ions were completely replaced by the Ca2+ ions. The crys tal symmetry of the (Sr, Ca) (Ga0.5Ta0.5)O-3 perovskites corresponding ly changed from cubic to orthorhombic with increasing Ca content. Part ial B-site cation ordering occurred when 10-50 mol% Ca2+ ions were inc orpolated in the A-site Sr2+ ions. The A-site cation substitution caus ed a very slight change in dielectric constant (epsilon(r)) at microwa ve frequencies, suggesting a little effect of the substitution on the ionic polarization of the perovskite structure. A substantial lowering in microwave Q-value observed for the solid solutions containing 10-2 0 mol% Ba2+ or Ca2+ ions might be related to the lack of long-range st ructure ordering. Temperature coefficient of epsilon(r) at 1 MHz chang ed from positive high values of the Ca2+-containing perovskites to nea rly zero for compounds with 20-40 mol% Ba2+ ions. This change was disc ussed in relation to the structual strain of (Ga, Ta)O-6 octahedra in the compounds.