Variable-range-hopping conductivity in high-k Ba(Fe0.5Nb0.5)O3 ceramicsShanming Ke, Peng Lin, Huiqing Fan, Haitao Huang, Xierong ZengJournal of Applied Physics2013/9/14,114(10)Abstract The dielectric and transport properties of Ba(Fe0.5 Nb 0.5)O3 ceramics have been investigated in a temperature range of 140–300 K and a frequency range of 1 Hz–10 MHz. The temperature dependence of bulk dc conductivity does not feature an Arrhenius behavior, but indicates a variable-range-hopping mechanism. The observed low temperature relaxation can be perfectly described by a polaronic model, which indicates that the dielectric relaxation is intimately related to the hopping motion caused by localized charge carriers.
Mean-field approach to dielectric relaxation in giant dielectric constant perovskite ceramicsShanming Ke, Peng Lin, Haitao Huang, Huiqing Fan, Xierong ZengJournal of Ceramics2013/8/25,2013(2013)Abstract The dielectric properties of CaCu3Ti4O3 (CCTO) and A2FeNbO6 (AFN, A= Ba, Sr, and Ca)
giant dielectric constant ceramics were investigated in the frequency range from 1 Hz to 10
MHz. The relaxation properties can be perfectly described by a polaron model, indicating
that the dielectric relaxation is intimately related to the hopping motion caused by localized
Antiferroelectric-like properties and enhanced polarization of Cu-doped K0.5Na0.5NbO3 piezoelectric ceramicsShanming Ke, HT Huang, HQ Fan, HK Lee, LM Zhou, Y-W MaiApplied Physics Letters2012/8,101(8)Abstract Abnormal evolution of ferroelectric hysteresis (P-E) loops was observed in Cu-doped K0.5Na0.5NbO3 (KNN) ceramics. The 1 mol. % Cu-doped fresh sample exhibited double-loop-like characteristics, while the 1.5 and 2 mol. % Cu-doped KNN ceramics showed normal single loops. Electron paramagnetic resonance spectra verified the formation of non-switchable (Cu′′′Nb−V∙∙O) ′ (DC1) and non-polar (V∙∙O−Cu′′′Nb−V∙∙O)∙ (DC2) defect complexes in these ceramics. According to the experimental results, it is suggested that DC1 would provide the driving force for domain back-switching, leading to the double P-E loops, while DC2 would contribute to the space charges.Dielectricaging behaviors of the samples also supported this mechanism. It is the competition between the DC1 and DC2 defect complexes that induced the observed compositional evolution of P-E loops in the Cu-doped KNN ceramics.