Dong-Soo Paik

Microstructure and Electrical Properties of Amorphous Films Grown on Cu/Ti/ /Si Substrates using RF Magnetron Sputtering

Amorphous Bi5Nb3O15 (BNO) films were grown at room temperature (RT) on a Cu/Ti/SiO2 /Si substrate using radio frequency magnetron sputtering. All the films were well formed on the Cu electrode with a sharp interface between the film and the electrode. The dielectric constant of the amorphous BNO film grown under 25 W was 46, with a low dissipation factor of 2.7% at 100 kHz. This film exhibited a low leakage current density of 5.5 × 10-8 A/cm2 at 4.5 V and a large breakdown voltage of 7.2 V. However, the electrical properties deteriorated as the sputtering power and the growth temperature increased due to the increased surface roughness; this was because a film with a rough surface generally has a larger surface area, and there can be electric field intensification at surface asperity, which degrade the electrical properties of the film. In addition, the electrical properties were not influenced by the oxygen partial pressure (OPP) because the variation of OPP during the growth of the films did not affect their surface roughness. The amorphous BNO film grown on the Cu/Ti/SiO2/Si substrate at RT under 25 W may be a good candidate material for an embedded capacitor.

Microstructure and Electrical Properties of Amorphous

Amorphous Bi5Nb3O15 (BNO) films were grown at room temperature (RT) on a Cu/Ti/SiO2 /Si substrate using radio frequency magnetron sputtering. All the films were well formed on the Cu electrode with a sharp interface between the film and the electrode. The dielectric constant of the amorphous BNO film grown under 25 W was 46, with a low dissipation factor of 2.7% at 100 kHz. This film exhibited a low leakage current density of 5.5 × 10-8 A/cm2 at 4.5 V and a large breakdown voltage of 7.2 V. However, the electrical properties deteriorated as the sputtering power and the growth temperature increased due to the increased surface roughness; this was because a film with a rough surface generally has a larger surface area, and there can be electric field intensification at surface asperity, which degrade the electrical properties of the film. In addition, the electrical properties were not influenced by the oxygen partial pressure (OPP) because the variation of OPP during the growth of the films did not affect their surface roughness. The amorphous BNO film grown on the Cu/Ti/SiO2/Si substrate at RT under 25 W may be a good candidate material for an embedded capacitor.

\hbox{Bi}_{5}\hbox{Nb}_{3}\hbox{O}_{15}

A piezoelectric motor capable of omni-directional movements has been developed to apply for robot joints, eyes, and precision positioning stage. The piezoelectric actuator has a simple structure of a cone type consisting of two piezoelectric ring-typed ceramics with electrodes divided into four segments and stainless steel elastic bodies. Before manufacturing the piezoelectric motor, the admittance characteristics and displacements of the actuator as a function of frequency were simulated. Elliptical motions of the actuator were created at several frequencies between the longitudinal and transverse resonance frequencies. The actual motor with alumina ball exhibited nice performance using a driving circuit with two rotary encoders and a PID controller. The moving element was omni-directionally operated at a driving frequency of 53.8 kHz and an output voltage of 280 V(p-p). The developed motor enables the moving element to move to a desired position with a resolution of 1.2 degrees/pulse, an angular velocity of 4 rad/s, and a thrust force of 200 g.

Films Grown on Cu/Ti/

In this paper, we present design and analysis of the omni-directional linear piezoelectric actuator which was consisted of one actuator using the half-wave vibrator. Through calculating vibration speeds on each sector of the actuator, the displacement of contact point of the actuator is theoretically confirmed to be about 33 nm. To confirm an applicable possibility of omni-directional linear piezoelectric actuator, elliptical motion for linear movement, displacement of the tip, changing directions and admittance characteristics are simulated by ATILA. Compared with theoretical result, we obtained similar data with displacement of 32.5 nm at contact point. And then the actuator is simulated elliptical trajectories for linear motions and changing directions according to combination of input signal.

\hbox{SiO}_{2}

The 0.95NKN-0.05CaTiO3 (0.95NKN-0.05CT) ceramics showed the high piezoelectric properties of d33=241, kp=0.41 and e3T/eo=1316. Therefore, the 0.95NKN-0.05CT ceramic is considered to be a promising candidate for lead-free piezoelectric material. However, its sintering temperature was high and Na2O evaporation occurred. Moreover, Na2O evaporation decreased the specimen resistivity and thus the poling efficiency. Therefore, the sintering temperature of this material needs to be decreased before it gains practical application. Moreover, the decreased sintering temperature is required to allow its application to multilayer devices. In this work, CuO was used to lower the sintering temperature of the 0.95NKN-0.05CT ceramics and variations of microstructure and piezoelectric properties of 0.95NKN-0.05CT ceramics were investigated with CuO addition. The piezoelectric properties of the specimens were considerably influenced by the relative density, grain size and liquid phase amount. The high piezoelectric properties of d33 = 200 pC/N, kp = 0.37, e3T/eo = 1173 and Qm = 350 were obtained for the 0.95NKN-0.05CT ceramics containing 2.0 mol% CuO sintered at 960 oC for 10 h.

/Si Substrates Using RF Magnetron Sputtering

In this study, in order to develop low loss multilayer piezoelectric actuator, PZN-PZT ceramics were fabricated using , CuO and ZnO as sintering aids, their structural, piezoelectric and dielectric characteristics were investigated according to the amount of ZnO addition, At the sintering temperature of , the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant() and piezoelectric constant() of 0.4 wt% ZnO added specimen (sintered at ) showed the optimum value of , 0.535, 916, 1399, 335 pC/N respectively. Taking into consideration above piezoelectric properties of the specimen sintered at low temperature, it was concluded that PZN-PZT ceramics using 0.4 wt% ZnO as additive showed the optimum characteristics as the composition ceramics for low loss multilayer piezoelectric actuator application.

Dynamic properties of an omni-directional piezoelectric motor for precision position control

In this study, multilayer piezoelectric transformer was manufactured using the PMN-PNN-PZT ceramic and then the electrical characteristics were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at the vicinity of 75 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the multilayer piezoelectric transformer showed the temperature rise of less than at the output power of 20 W. As the results, the multilayer piezoelectric transformer manufactured at low co-firing temperature of using PMN-PNN-PZT ceramics could be stably driven as the step-down transformers.

Design and analysis of omni-directional linear piezoelectric actuator

Dielectric and piezoelectric properties of PMN-PZT ceramics with a high mechanical quality factor and a low temperature sintering temperature were investigated as a function of PZN substitution in order to develop multilayer piezoelectric transformer for AC-DC converter. Multilayer piezoelectric transformers were subsequently manufactured using the PMN-PZN-PZT ceramic offering the optimal behavior and then the electrical performance were invetigated. At the sintering temperature of , density, electromechanical coupling factor, mechanical qualify factor and dielectric constant of 8 mol% PZN substituted specimen were , 0.524, 1573 and 1455, respectively. The PZN substitution caused a increase in the dielectric constant and the electromechnical coupling factor. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at near the resonant frequency of 76.55 kHz and increased according to the increase of load resistance. The multilayer piezoelectric transformer with the output impedance coincided with the load resistance showed the temperature increase of less than at the output power of 10 W. Based on the results, the manufactured multilayer transformer using the low temperature sintered PMN-PZN-PZT ceramics can be stably driven for both step-up and down transformers.

Low temperature sintering and piezoelectric properties of lead-free (1-x) (Na0.5K0.5)NbO3-xCaTiO3 ceramics

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PMN-PZT ceramics were manufactured with the variations of sintering times, and their microstructural, piezoelectric and dielectric properties were investigated. LiCO and BiO were used as sintering aids and the specimens were sintered during 30, 60, 90, 120, 150, and 180 minutes, respectively. At the specimen sintered during 90 minute, mechanical quality factor(Qm), electro-mechanical coupling factor(kp) and dielectric constant were showed the optimum values of 2,356, 0.504 and 1,266, respectively.