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Effects of Calcium Substitution on the Structural and Microwave Dielectric Characteristics of [(Pb 1− x Ca x ) 1/2 La 1/2 ](Mg 1/2 Nb 1/2 )O 3 Ceramics
Author(s) -
Liu ChinLin,
Wu TaiBor
Publication year - 2001
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2001.tb00831.x
Subject(s) - dielectric , calcium , analytical chemistry (journal) , microwave , perovskite (structure) , lattice constant , chemistry , chemical composition , composition (language) , materials science , temperature coefficient , crystallography , mineralogy , diffraction , metallurgy , optics , linguistics , physics , philosophy , optoelectronics , organic chemistry , chromatography , quantum mechanics , composite material
The effects of calcium substitution on the structural and microwave dielectric characteristics of [(Pb 1− x Ca x ) 1/2 La 1/2 ](Mg 1/2 Nb 1/2 )O 3 ceramics (with x = 0.01–0.5) were investigated. All the materials were observed to have an ordered A(B 1/2 ′ B 1/2 ″ )O 3 ‐type perovskite structure; however, the space group of the structure changed from Fm 3 m to Pa 3 as the calcium content increased to x = 0.1, and then from Pa 3 to R 3¯ at the x = 0.5 composition. During the structural evolution, the lattice parameter of the perovskite cell decreased linearly, and the dielectric constant ( k ) also decreased, from k = 80 to k = 38. However, the product of the quality factor and the resonant frequency ( Q × f ) increased from 50 000 GHz to 90 000 GHz as the calcium content increased. Also, the temperature coefficient of resonant frequency (τ ƒ ) gradually changed from 120 ppm/°C to −40 ppm/°C as the calcium content increased. At the x = 0.3 composition, a combination of properties— k ∼ 50, Q × f ∼ 86 000 GHz, and τ ƒ ∼ 0 ppm/°C—can be obtained.