Densification Based on Control of Volatile Mass of Potassium and Sodium in $(K_{1/2}\;Na_{1/2})NbO_3$ Ceramics

(1)

-2006 POWDER METALLURGY World Congress

PC11-W-14

PC11-W-15

Densification Based on Control of Volatile Mass of Potassium and

Sodium in (K

1/2

Na

1/2

)NbO

3

Ceramics

Y. H. LEE*,**_{, J. H. Cho}*_{, B. I. Kim}*_{, D. G. Choi} **

* Department of Ceramic Building Materials Research, Korea Institute of Ceramic Engineering and Technology, Seoul 153-023, KOREA

** Department Ceramic Engineering, Hanyang University 17 Haengdang-Dong, Seongdong-Gu, Seoul 133-791, KOREA

The regulation on environmental preservation has been strengthened in the global scale. Recently lead free ceramic systems are intensely studied in order to find environmentally friendly piezoelectric ceramics and replace the widely used lea d-based piezoelectric ceramics. In this paper, we concentrated on densification of potassium-sodium niobate ceramics by planetry ball mill and adding dopants. Because, in earlier work on potassium-sodium niobate, air sintering requires long soaking periods for sufficient densification, ceramics was sintered by hot pressing.

In this study, potassium-sodium niobate based ceramic have been synthesized by convensional solid state reaction. The effects of planetary ball mill and dopant addition on the densification and piezoelectric properties were investigated by XRD, SEM, impedance analyzer, hysteresis-loop measurement and I-V measurement.

The experimental results suggest that potassium-sodium niobate ceramics sintered to yield body with relative densities greater than 95% in air and potassium-sodium niobate ceramics is considered an advanced ferroelectric material for high frequency application.

Kinetics of Fe

3

O

4

Formation from

β-FeOOH in the Presence of Urea

Dae-Gyu Shin1,2_{, Young-Keun Jeong}1_{, Jong-Heun Lee}2_,

Kyung-Sik Oh3_{, Doh-Hyung Riu}1 1

Nano Materials Team, KICET(Korea Institute of Ceramic Engineering and Technology),

2

Division of materials Science and Engineering, Korea University,

3

School of Advanced Materials Engineering, Andong National University.

Fe3O4 can be prepared from the reaction of β-FeOOH and FeCl2 in the presence of urea solution of pH above 6. The

transformation kinetics can affect the size of Fe3O4 formed through the dissolution and reprecipitation process.

In this study, we have prepared a various size of β-FeOOH by the hydrolysis of FeCl3 aqueous solution having different

concentration level with or without the presence of the urea. The transformed size of Fe3O4 was directly related to the size of

β-FeOOH. At a fixed concentration of FeCl3+FeCl2, to select an exact reaction time to put an external precipitation agents

was an important reaction variable to get a proper size ranges of Fe3O4. By the control of this transformation kinetics, we have

obtained magnetite nanoparticles with 10~50 nm. These superparamagnetic nanoparticles could be used in biomedical applications.