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AC Impedance Spectroscopy of CaF 2 ‐doped AlN Ceramics
Author(s) -
Lee HyeonKeun,
Lee Hyun Min,
Kim Do Kyung
Publication year - 2014
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/jace.12685
Subject(s) - materials science , grain boundary , microstructure , electrical resistivity and conductivity , ceramic , nitride , dielectric spectroscopy , amorphous solid , doping , composite material , mineralogy , grain size , analytical chemistry (journal) , crystallography , chemistry , optoelectronics , electrode , layer (electronics) , electrochemistry , chromatography , electrical engineering , engineering
The electrical conductivity of CaF 2 ‐doped aluminum nitride ( AlN ) ceramics was characterized at high temperatures, up to 500°C, by AC impedance spectroscopy. High thermal conductive CaF 2 ‐doped AlN ceramics were sintered with a second additive, Al 2 O 3 , added to control the electrical conductivity. The effects of calcium fluoride ( CaF 2 ) on microstructure and related electrical conductivity of AlN ceramics were examined. Investigation into the microstructure of specimens by TEM analysis showed that AlN ceramics sintered with only CaF 2 additive have no secondary phases at grain boundaries. Addition of Al 2 O 3 caused the formation of amorphous phases at grain boundaries. Addition of Al 2 O 3 to CaF 2 ‐doped AlN ceramics at temperatures 200°C–500°C revealed a variation in electrical resistivity that was four orders of magnitude larger than for the specimen without Al 2 O 3. The amorphous phase at the grain boundary greatly increases the electrical resistivity of AlN ceramics without causing a significant deterioration of thermal conductivity.