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Sintering Characteristics in the BaTiO 3 –Nb 2 O 5 –Co 3 O 4 Ternary System: II, Stability of So‐called “Core–Shell” Structure
Author(s) -
Chazono Hirokazu,
Kishi Hiroshi
Publication year - 2000
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.1151-2916.2000.tb01155.x
Subject(s) - microstructure , sintering , materials science , differential scanning calorimetry , diffusion , ternary operation , analytical chemistry (journal) , niobium , thermal diffusivity , thermal stability , crystallography , mineralogy , chemical engineering , chemistry , metallurgy , thermodynamics , physics , chromatography , computer science , programming language , engineering
The sintering characteristics and the reaction of additives with BaTiO 3 (BT) were examined for two materials having Nb‐rich composition (Comp.N) and Co‐rich composition (Comp.C) to elucidate the relation between the stability of the core–shell microstructure and the Nb/Co ratio in the BT–Nb 2 O 5 –Co 3 O 4 system. TEM observation revealed that the concentration gradient of Nb and Co existed in the shell region although Nb and Co macroscopically distributed homogeneously. X‐ray diffraction analysis showed that the shell formation preceded the densification and completed at about 1280°C for both Comp.N and Comp.C as determined from differential scanning calorimetry. A diffusion couple experiment disclosed that Co had a larger diffusivity than Nb and that the diffusion of Co was suppressed when the sample was codoped with a sufficient amount of Nb. On the basis of these experimental results, new mechanisms of the formation and collapse of core–shell structure in the BT–Nb 2 O 5 –Co 3 O 4 system were proposed.