Premium
Formation, Defect Structure, and Electrical Properties of La 3+ ‐Doped M‐Type Calcium Ferrite Prepared by Coprecipitation
Author(s) -
Fang TsangTse,
Lee KuoTong
Publication year - 1989
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.1151-2916.1989.tb06080.x
Subject(s) - coprecipitation , thermogravimetric analysis , activation energy , polaron , ferrite (magnet) , differential thermal analysis , conductivity , materials science , analytical chemistry (journal) , doping , electrical resistivity and conductivity , thermal conduction , mineralogy , chemistry , inorganic chemistry , composite material , physics , electrical engineering , optoelectronics , organic chemistry , chromatography , quantum mechanics , diffraction , optics , engineering , electron
The reaction process and the optimum preparation conditions of the M‐type calcium ferrite by the chemically coprecipitated method were studied using differential thermal, thermogravimetric, and X‐ray analyses. It is found that the formation mechanism using the coprecipitated method is the same as that of the solid‐state reaction, and the precursor CaO·2Fe 2 O 3 cannot be avoided, but it could be formed at lower temperature. The defect structure based on the replacement of Ca 2+ by La 3+ , the charge compensation by Fe 2+ , and release of oxygen is supported by the DTA/TGA and conductivity data. The conductivity is suggested to occur through a hopping mechanism. The estimated values of the activation energy based on the small‐polaron conduction are 0.34 to 0.44 eV in the high‐temperature region and 0.029 to 0.049 eV in the low‐temperature region. The preexponential factor depends exponentially on the fraction of the M phase in the specimen.