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Base‐Metal‐Electroded BaTiO 3 Capacitor Materials with Duplex Microstructures
Author(s) -
Lin INan,
Yang WeiChun,
Hu ChenTi
Publication year - 2004
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.1551-2916.2004.00851.x
Subject(s) - dielectric , materials science , ceramic capacitor , capacitance , capacitor , dopant , microstructure , composite material , metal , doping , optoelectronics , metallurgy , electrode , voltage , electrical engineering , chemistry , engineering
The effect of dopants and processing conditions on the dielectric properties of base‐metal‐electroded materials was investigated. BaTiO 3 materials simultaneously doped with MgO and Y 2 O 3 additives can achieve small capacitance variation (Δ C / C ), which meets the X7R specification, when the proportion of additives is abundant enough and the materials are not over‐fired. Presumably, small Δ C / C values of thus obtained materials are the result of the formation of core–shell structure, which requires stringent control of material processing conditions. In contrast, X7R‐type materials can be obtained in a much wider processing window, when prepared by mixing two BaTiO 3 materials of suitable dielectric constant–temperature ( K – T ) characteristics. Duplexed materials prepared from these two end‐point BaTiO 3 materials with ratios ranging from 3:1 to 1:2 exhibit K – T behavior within the X7R specification, provided that one of the components possesses flat K – T behavior. Moreover, the dielectric properties of these materials were simulated using a simplified microstructural model. Simulation results indicate that the effective dielectric constant of core–shell materials, ( K e ) CS , varies significantly not only with the dielectric properties of cores and shells, but also with the shell‐to‐core thickness ratio, whereas the effective dielectric constant of duplexed materials, ( K e ) D , can be maintained at a very small Δ C / C value for a wide range of end‐point constituent ratios, which agrees very well with the measured K – T properties for the materials.