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Microwave Dielectric Characteristics of Aluminum Magnesium Tantalate Based High Q Ceramics
Ji-WonChoi,Hwack-JooLee,Seok-JinYoon,Hyun-JaiKim 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.4
The microwave dielectric characteristics of (1-x)(Al1/2Ta1/2)O2-x(Mg1/3Ta2/3)O2 (0 x 1.0) ceramics were investigated by crystal structure, variations of ionic polarizability, and microstructures. As x increased, (1-x)(Al1/2Ta1/2)O2-x(Mg1/3Ta2/3)O2 transformed to tetragonal structure. Because the ionic radius of [Mg1/3Ta2/3]4+ was slightly bigger than one of [Al1/2Ta1/2]4+, the cell parameters increased with increase of (Mg1/3Ta2/3)O2 concentration and coincided with prediction of the molecular additivity rule. As x increased, the compositions revealed ordered phase and were of single phase above 60 mol%. The increase of the ordered phase and grain size enhanced the Q and when ordering was completed at x over 0.6, the grain size was major factor for the increase in the Q. Though the grain size increased, however, the porosity deteriorated the Q. Therefore, the Q depended on the order/disorder, the porosity, and the grain size in regular order.
Bender Typed Piezoelectric Multilayer Actuator
Byung-GukAhn,Dong-KyunLee,Deuk-YoungHan,강종윤,Ji-WonChoi,Hyun-JaiKim,Seok-JinYoon 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.3
A bender typed multilayer actuator (BMA) for decreasing the depolarization effect was designed and fabricated. Unlike bimorph and multimorph actuators in which depolarization occurred, the BMA did not generate depolarization because the polarization and the electric field directions are the same. The simulated results indicate that higher displacement of the BMA can be achieved by increasing input voltage. Compared with the multimorph actuator, the proposed actuator is expected to extend a life time as well as acceptable voltage range.
Min-ChulKim,Ji-WonChoi,Chong-YunKang,Seok-JinYoon,Hyun-JaiKim,KiHyunYoon 한국전기전자재료학회 2002 Transactions on Electrical and Electronic Material Vol.3 No.1
The effects of substrate temperatures and annealing temperatures on the microstructures and ferroelectric properties of PbZr0.52Ti0.48O3 (PZT) thin films prepared by pulsed laser deposition (PLD) were investigated. For this purpose, the PZT films were deposited at various substrate temperatures (400∼600℃) with post annealing process in oxygen atmosphere. The single perovskite phase was formed at the deposition temperature of 500 to 550℃ without post annealing and the PZT films deposited below 500℃ formed the single phase with post annealing at 650℃. The grain size of the films increased and the grain boundary of the films was clearly defined as the substrate temperature increased from 400 to 550℃. The remnant polarization (Pr) and the coercive field (Ec) of the films deposited at 550℃ and annealed at 650℃ were 34.3 μC/cm2 and 60.2 kV/cm, respectively.