Hydroxyl Defect-Dielectric Property Relations in Reoxidation of Acceptor-Doped (Ba Ca)(Ti Zr)O3 Bulk Ceramics

  • 高 育儒

Student thesis: Doctoral Thesis


Dielectric property and degradation behavior of acceptor (Sc or Y)-doped (Ba Ca)(Ti Zr)O3 ceramics sintered in moist reducing atmosphere and subsequently re-oxidized in dry or wet atmospheres was contrasted In moist firing atmosphere water vapor was found to react with oxygen vacancies forming positively charged hydroxyl defects on regular oxygen sites in the crystal lattice Proton hopping is considered to raise the ionic conductivity significantly Therefore hydroxyl defects in turn influence the grain conduction Hydroxyl defects are also considered to be responsible for alternations of the dielectric maximum at the Curie point On the other hand the degradation behavior critically depends on the water vapor incorporation the time to degradation systematically decreased with the incorporation of hydroxyl defects The electrical conductivity was investigated by means of impedance spectroscopy (IS) to determine properties such as grain and grain boundary conductivity grain boundary potential barrier height and space charge layer thickness Furthermore transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) were applied to consider microstructure microchemistry and oxygen stoichiometry changes
Date of Award2016 Aug 4
Original languageEnglish
SupervisorChi-Yuen Huang (Supervisor)

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