• Applied Microscopy
• /
• v.42 no.3
• /
• pp.164-173
• /
• 2012

The relaxor ferroelectric feature in lead-free perovskite oxides, where the dipoles are randomly oriented and they can be feasibly aligned parallel to the external bias, is attracting lots of attention in the field of piezoelectric materials science, since it is one of candidates to replace the toxic lead-based materials that are still being commercially used. However, the origin of relaxor characteristic and its related atomic structure are still ambiguous. In this study, $Na_{1/2}Bi_{1/2}TiO_3$, chosen as a model relaxor system, was found to exhibit a cationic-disordered atomic structure; and furthermore the nonpolar atomic structure and its related oxygen tilting were ascertained via annular bright field imaging skill. We also found that this cationic disordering gives rise to the local formation of atomic vacancies.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.35-35
• /
• 2003

Recent progress in the integration of the ferroelectric random access memories (FRAM) has attracted much interest. Strontium bismuth tantalate(SBT) is one of the most attractive materials for use in nonvolatile-memory applications due to low-voltage operations, low leakage current, and its excellent fatigue-free property. High-density FRAMs operated at a low voltage below 1.5V are applicable to mobile devices operated by battery. SBT films thinner than 0.1 #m can be operated at a low voltage, because the coercive voltage (Vc) decreases as the film thickness is reduced. In addition, the thickness of the SBT film will have to be reduced so it can fit between adjacent storage nodes in a pedestal type capacitor in future FRAMs.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.5
• /
• pp.214-220
• /
• 2005

The ferroelectric properties of the $Pt/PZT(Pb(Zr,Ti)O_3)/Pt$ capacitors are severely degraded when they are annealed in hydrogen-containing environment. Hydrogen atoms created by the catalytic reaction of Pt top electrode during annealing in hydrogen ambient penetrate into PZT films and generate oxygen vacancies by the reduction of the PZT films, which is likely to cause the degradation. The degree of hydrogen-induced degradation and the direction of voltage shift in P-E curves of the pre-poled PZT capacitors after annealing in hydrogen ambient is dependent on the polarity of the pre-poling voltage. This implies that oxygen vacancies causing hydrogen induced degradation are generated by hydrogen ions having a polarity. The degraded ferroelectricity of the PZT capacitors can be effectively recovered by the shift of oxygen vacancies toward the Pt top electrode interface during post-annealing in oxygen environment with applying negative unipolar stressing.

• The Korean Journal of Ceramics
• /
• v.6 no.3
• /
• pp.262-266
• /
• 2000

We investigated the effect of the grain size on the photovoltaic current in (Pb$_{1-x}$La$_x$)TiO$_3$ceramics, and the photoinduced domain switching in (Pb$_{0.85}$La$_{0.15}$)TiO$_3$and BaTiO$_3$ceramics. These behaviors in ferroelectric ceramics were attributed to the grain boundary at which photoexcited electrons were trapped. As the charged grain boundary acted as an electro-potential barrier which impeded the movement of electrons, the photovoltaic current showed a peak at a critical grain size. The space charge field built by the electrons trapped at the grain bound-aries was accounted for the photoinduced domain switching, and AE experimental results support well this account.

• Journal of the Korean Ceramic Society
• /
• v.44 no.5 s.300
• /
• pp.141-143
• /
• 2007

Nanotubes and microtubes of ferroelectric lead zirconate titanate (PZT) were synthesized by means of a simple and convenient process called a template-wetting process. Nanoporous alumina and macroporous Si were used as template materials to fabricate the corresponding tubes. For the improvement of the wetting properties of the wetting solution, the PZT solution was mixed with a polymer. The polymer was removed completely during annealing. The grain growth processes of the PZT nanotubes during baking and furnace annealing were examined by means of field emission electron microscope (FE-SEM) and X-ray diffractometry (XRD).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.30-33
• /
• 2001

This thesis deal with ferroelectric and ferrimagnetic materials, PZT/Ferrite ceramics. We conducted test of magnetical and electrical measurement. From this measurement, We obtained tunability and we can control characteristic impedance($Z_0$) from permeability($\mu$) and dielectric constant($\varepsilon$) for impedance matching in transmission line.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11a
• /
• pp.30-33
• /
• 2001

This thesis deal with ferroelectric and ferrimagnetic materials, PZT/Ferrite ceramics. We conducted test of magnetical and electrical measurement. From this measurement, We obtained tunability and we can control characteristic impedance(Z$_{0}$) from permeability($\mu$) and dielectric constant($\varepsilon$) for impedance matching in transmission line.e.

• Electrical & Electronic Materials
• /
• v.18 no.12
• /
• pp.11-17
• /
• 2005

• Proceedings of the Korean Vacuum Society Conference
• /
• 1994.06a
• /
• pp.159.1-159
• /
• 1994

• Proceedings of the Korean Vacuum Society Conference
• /
• 1994.06a
• /
• pp.159.2-159
• /
• 1994