Publication Date:
2012-04-15
Description:
Perovskite ceramics of Ba [ Ti 1− x ( Co 0.5 W 0.5 ) x ] O 3 ( x = 0.40–0.90) were synthesized by a conventional solid-state reaction method. Crystal phase, microstructure, and microwave dielectric property of the ceramics were investigated. A phase transition from simple cubic ( x = 0.40–0.55) to hexagonal and then to cubic double pervoskite ( x = 0.75–0.90) was detected. A single hexagonal perovskite structure ( P6 3 /mmc ) was obtained at 1425°C and stabilized at room temperature only at x = 0.61. For ceramics x = 0.55–0.60 and x = 0.62–0.75, they are mixtures that consisted of cubic and hexagonal perovskites. With increasing x , Qx f increased from 2800 to 20 700 GHz, whereas dielectric constant (ε r ) decreased from 65 to 18, and temperature coefficient of resonant frequency (τ ƒ ) decreased from 44 to −17 ppm/°C. Hexagonal perovskite (ε r = 18, Qx f = 7700 GHz, τ ƒ = −14 ppm/°C) had decreased ε r , τ ƒ and increased Qx f values, compared with the cubic perovskite phases. The phase formation and the relationship between structures and microwave dielectric properties were discussed.
Print ISSN:
0002-7820
Electronic ISSN:
1551-2916
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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