Browsing by Author "Chiu, S.-J."

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Dielectric properties in lead-free piezoelectric (Bi0.5Na0.5)TiO3-BaTiO3 single crystals and ceramics
(2014) Chen, Cheng-Sao; Tu, Chi-Shun; Chen, Pin-Yi; Ting, Yi; Chiu, S.-J.; Hung, C.-M.; Lee, H.-Y.; Wang, S.-F.; Anthoninappen, J.; Schmidt, V. Hugo; Chien, R. R.
The 0.93(Bi0.5Na0.5)TiO3–0.07BaTiO3 (BNB7T) piezoelectric single crystals and ceramics have been grown respectively by using the self-flux and solid-state-reaction methods. The real (ε′) and imaginary (ε″) parts of the dielectric permittivity of BNB7T crystals and ceramics were investigated with and without an electric (E) poling as functions of temperature and frequency. The BNB7T crystal shows a stronger dielectric maximum at Tm~240 °C than the ceramic at Tm~300 °C. The dielectric permittivity of BNB7T ceramic shows an extra peak after poling at an electric field E=40 kV/cm in the region of 80–100 °C designated as the depolarization temperature (Td). A wide-range dielectric thermal hysteresis was observed in BNB7T crystal and ceramic, suggesting a first-order-like phase transition. The dielectric permittivity ε′ obeys the Curie–Weiss equation, ε′=C/(T−To), above 500 °C, which is considered as the Burns temperature (TB), below which polar nanoregions begin to develop and attenuate dielectric responses.
Raman spectra and structural stability in B-site manganese doped (Bi0.5Na0.5)0.925Ba0.075TiO3 relaxor ferroelectric ceramics
(2015-11) Anthoniappen, J.; Tu, Chi-Shun; Chen, Pin-Yi; Chen, Cheng-Sao; Idzerda, Yves U.; Chiu, S.-J.
Soft X-ray absorption (XAS), transmission electron spectroscopy (TEM), Raman spectroscopy, and synchrotron XRD have been studied in B-site 0–2 mol% manganese (Mn) doped (Bi0.5Na0.5)0.925Ba0.075TiO3 (BN7.5BT) relaxor ferroelectric ceramics. High-resolution synchrotron XRD and TEM reveal two phase coexistence of rhombohedral R3c and tetragonal P4bm structures in 0 and 0.2%, and an orthorhombic structure in 1 and 2% Mn-doped BN7.5BT at room temperature. Raman spectra of 0% Mn reveal structural transition from two phase coexistence to tetragonal phase near 190 °C with a softening anomaly, while 0.2–2% Mn-doped BN7.5BT show softening behavior near 290 °C upon heating. Raman spectra and synchrotron XRD indicate that Mn doping can enhance structural thermal stability in BN7.5BT ceramics.