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Prof.Yoon's research work has been devoted to the chemical synthesis, ceramic
processing, microstructure improvement and electrical property measurements and
improved electrical properties of electronic ceramic materials
First,
the microwave dielectric mechanisms of the ceramic materials such as complex
perovskites for wireless communications have been investigated on the basis of
order-disorder and far IR reflectivity to improve dielectric loss.The
intrinsic dielectric loss at microwave frequencies measured by the post
resonant method could be
compared
with that calculated from the dispersion parameters obtained by the infrared
reflectivity spectra. And the concept of bond valence has been applied to
evaluate the temperature coefficient of the resonant frequency (TCF) of the
complex perovskite compounds. Both approaches have been tried first by Prof.
Yoon's laboratory.
Second,
preparation processing and electrical properties of the thin films for relaxors
and ferroelectric memories have been investigated using a sol-gel method.
Microstructures and dielectric properties have been improved by adapting
processing parameters such as complex agent, film formation and heating
processes. The electric fatigue behavior in the antiferroelectric and
ferroelectric thin films has been discussed in terms of structural defects from
the induced stress during switching cycles as well as the electric defects. The
novel method introduced the fatigue-free antiferoelectric buffer in the
ferroelectric capacitors by modifying the composition of ferroelectric thin
film surfaces can minimize the electric fatigue in the conventional PZT-based
materials with Pt electrode.
Third,
the molten salt synthesis (MSS) method adopted by Prof. Yoon's laboratory has
several unique characteristics compared to other methods like the conventional
mixed oxides, coprecipitation and sol-gel methods. The MSS method can be one of
the simplest methods for obtaining highly reactive powders of a single phase at
low temperatures in shorter soaking times, in which the molten salt is used as
a reaction aid.
Fourth,
the non-ferroelectric materials have been proved to be promising alternatives
for the bright electron gun with double occurrences of emission compared to the
ferroelectrics.
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Current Research Topics
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1. Microwave Dielectrics (Processing and Electrical behavior)
- Microwave Dielectric Resonators (Ba(Mg1/3
Ta2/3)O
3, Li2
O-CaO-Sm2
O3
-TiO2
, (Zr0.8
Sn0.2)TiO
4,
(Pb,Ca)(Fe,Nb,Ta)O3
)
- Low temperature sintering dielectrics for LTCC
(BiNbO4)
- Thin film (CaTiO3-(Li,Sm)TiO3)
- Mechanism of microwave dielectric loss, and
relationship between TCF and bond valence
2. Ferroelectrics (Processing and Electrical behavior)
- Shape Memory Ceramics ( PbY(ZrSnTi)O3, (PbBa)(ZrTi)O3,(PbBa)ZrO3 )
- Relaxors ( PMN-PT, PZSTN )
- Ferroelectric Memories (PZT, PZSTN, PLZT, BST thin films )
3. Electron Emission from Ferroelectrics Induced by Pulsed Electric Field
- Electron emission from PZT, PLZT ceramic and thin film cathode
- Effect of cathode structure on electron emission
4. Polymer Light Emitting Diode
- Preparation of PPV-TiO2 nanoparticle composites
- Electroluminescent behavior of ITO/PPV-TiO nanoparticle composites/Al
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