Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO3-Based Ceramics by Ge Substitution

Title
Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO3-Based Ceramics by Ge Substitution
Authors
하종윤윤석진정대용최지원
Keywords
Dielectric; Low temperature; Dielectric loss; BST
Issue Date
2010-08
Publisher
Japanese journal of applied physics
Citation
VOL 49, 071505-1-071505-4
Abstract
Multilayer microwave dielectric materials with low sintering temperature are required for microwave phase shifters, filters, and true-time delay devices. We investigated the sintering and dielectric properties of (Ba0:6Sr0:4)(Ti1-xGex)O3 (BSTG; 0:05 ≤ x ≤ 0:3) ceramics. As the Ge concentration was increased, the lattice constant of BSTG ceramics decreased, and Ba2Ge2TiO8, which is the liquid phase at low temperature, was formed. Ba2Ge2TiO8 liquid phase may increase the sintering density. The effect of Ge substitution is the decrease in the sintering temperature from over 1400 to 1150 ℃ in BST system ferroelectric ceramics. With increasing Ge concentration, the dielectric constant decreased from 2190 to 530, and the dielectric loss decreased up to 0.001 (at 1 MHz) with sintering at 1150 ℃ for 2 h. When Ge was substituted at 0.05 and 0.1 mol of Ti in the BST at 1150 ℃, the dielectric constant, dielectric loss, tunability, Curie temperature, and figure of merit were 2184 and 1529, 0.002 and 0.001, 27 and 23%, -11 and -18 ℃, and 135 and 230, respectively. These compositions show microwave dielectric properties comparable to those of (Ba0:5Sr0:5)TiO3 ferroelectrics, which are the important materials for tunable devices such as varactors, phase shifters, and frequency agile filters.
URI
http://pubs.kist.re.kr/handle/201004/37917
ISSN
0021-4922
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