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Grain Growth‐Controlled Giant Permittivity in Soft Chemistry CaCu 3 Ti 4 O 12 Ceramics
Author(s) -
Marchin Loïc,
GuillemetFritsch Sophie,
Durand Bernard,
Levchenko Andrey A.,
Navrotsky Alexandra,
Lebey Thierry
Publication year - 2008
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.1551-2916.2007.02174.x
Subject(s) - coprecipitation , materials science , eutectic system , ceramic , dielectric , permittivity , grain growth , grain size , grain boundary , phase (matter) , calcination , mineralogy , analytical chemistry (journal) , sintering , microstructure , chemical engineering , composite material , chemistry , catalysis , optoelectronics , organic chemistry , chromatography , engineering , biochemistry
We report a dielectric constant of up to 5.4 × 10 5 at room temperature and 1 kHz for CaCu 3 Ti 4 O 12 (CCTO) ceramics, derived from multiphase powders (coprecipitation products), made by a “chimie douce” (coprecipitation) method, and then sintered in air. The sintered products are pure‐phase CCTO ceramics. The high dielectric constant is achieved by tuning the size of grains and the thickness of grain boundaries. The grain growth is controlled by varying the concentration of excess CuO in the initial powder (calcined coprecipitation products) between 1 and 3.1 wt%. The dielectric constant of pure CCTO ceramics increases with the initial CuO concentration, reaching its maximum at 2.4 wt% of CuO. A further increase of excess CuO in powders results in a permittivity decrease, accompanied by the formation of CuO as a separate phase in the sintered products. The unusual grain growth behavior is attributed to a eutectic reaction between CuO and TiO 2 present in the initial powder.