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Effect of Oxygen Partial Pressure on the Dielectric Properties and Microstructures of Cofired Base‐Metal‐Electrode Multilayer Ceramic Capacitors
Author(s) -
Feng Qiquan,
McConville Caspar J.,
Edwards Doreen D.,
McCauley Daniel E.,
Chu Mike
Publication year - 2006
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.1551-2916.2005.00787.x
Subject(s) - materials science , dielectric , microstructure , grain boundary , ceramic capacitor , analytical chemistry (journal) , dopant , ceramic , sintering , mineralogy , composite material , capacitor , chemistry , doping , physics , optoelectronics , chromatography , quantum mechanics , voltage
The dielectric properties, dopant distributions, and microstructures of BaTiO 3 ‐based multilayer ceramic capacitors (MLCCs) sintered in H 2 –N 2 –H 2 O atmospheres with=10 −7.5 Pa (BMX‐7.5) and=10 −9.5 Pa (BMX‐9.5) were studied, and the effects of oxygen partial pressures were analyzed. Dielectric measurements showed that BMX‐7.5 had a lower dielectric constant at temperatures above 20°C, but a higher dielectric constant at temperatures below 10°C when compared with BMX‐9.5. The coexistence of core–shell and core grains was observed in bright field (BF) transmission electron microscopy images in both types of capacitors. Triple‐point and grain boundary phases were observed more frequently in BMX‐9.5 than in BMX‐7.5, and energy‐dispersive X‐ray spectrometer point‐by‐point analysis revealed that these second phases contained high concentrations of dopants such as Si, Y, and Ca. The dopant concentration in the shell regions in BMX‐7.5 was higher than that in similar regions in BMX‐9.5. Smeared and twisted grain boundaries with fringes observed in both types of MLCCs indicated that the shell regions in both samples were formed either by diffusion of foreign ions into BaTiO 3 or by crystallization of grain boundary and triple‐point liquid phases. It was deduced that the partial pressure of oxygen in the sintering atmosphere influenced the microstructures, dopant distributions, and core–shell ratios of the grains in these materials.