Yeong-Ho Jeong

Voltage gain characteristics of piezoelectric transformer using PbTiO3 system ceramics

Abstract PbTiO 3 system ceramics were suitable to be used for a piezoelectric transformer, operating in thickness extensional vibration mode because these are materials with large anisotropy of electromechanical coupling factor, k t / k p . In this paper, the (Pb 0.76 Ca 0.24 )[(Co 0.5 W 0.5 ) 0.04 Ti 0.96 ]O 3 +1.5 mol% MnO 2 ceramic system for piezoelectric transformers were manufactured. Its electromechanical coupling coefficients, k t of 49% and k p of near zero, which give rise to large anisotropic property, k t / k p , were obtained from the specimen sintered at 1150°C. A piezoelectric transformer that is 20 mm long, 20 mm wide and 3.1 mm thick was fabricated using this composition ceramic. Resonant frequencies of second thickness extensional vibration mode are 1.56 and 1.58 MHz at loading resistance 100 and 200 Ω, respectively. Maximum voltage gain of piezoelectric ceramics was 0.72 and 0.86 at resonant frequency of second thickness extensional vibration mode at loading resistance 100 and 200 [Ω], respectively.

Dielectric and Piezoelectric Properties of (K 0.5 Na 0.5 ) (Nb 0.97 Sb 0.03 )O 3 Ceramics Doped with K 4 CuNb 8 O 23

Visual displays have been widely used to gain information. However, it is evident that visual displays in handheld mobile devices can be limited in the delivery of the full feelings of people. Thus, a haptic interface with tactile feedback can play an important role in the delivery of accurate and obvious feelings between human and machine [1]. In addition, a tactile sensation is about five times faster than a visual one [2]. A vibrating motor [3], solenoid type actuator, and piezoelectric actuator have been generally used until now to generate haptic feeling in mobile devices. Piezoelectric actuators with the advantages of low power consumption and a fast response time can produce various kinds of vibration for haptic feelings [4]. Pb(Zr,Ti)O3 (PZT) composition ceramics, which have been widely utilized for piezoelectric device application, contain the toxicity of lead oxide. The use of these ceramics can cause serious environmental pollution and human health problems. In addition, it is very difficult to maintain the reproducibility of the original ceramic composition due to the fluctuation in composition of the ceramics caused by the rapid evaporation of PbO when sintered at temperatures above 1,000°C. Thus, PbO should be excessively added to prevent composition fluctuation in the manufacture of PZT system ceramics. It also can cause serious environmental problems. Therefore, it is necessary to develop new lead-free piezoelectric composition ceramics to replace PZT-based ceramics. Lead-free piezoelectric ceramics, such as tungsten bronze type, bismuth layered type, and alkaline niobate-based type ceramics, have been extensively studied for the replacement of lead-containing ceramics. However, it is difficult to obtain the dense lead-free piezoelectric ceramic using ordinary sintering methods due to the high volatility of alkaline elements at high temperatures. Therefore, the optimum sintering temperature plays an important role in obtaining excellent electrical properties. Accordingly, special manufacturReceived February 18, 2011; Revised March 16, 2011; Accepted March 17, 2011 Sang-ho Lee, Kab-Soo Lee, and Ju-Hyun Yoo Department of Electrical Engineering, Semyung University, Jecheon 390-711, Korea Dielectric and Piezoelectric Properties of (K0.5Na0.5) (Nb0.97Sb0.03)O3 Ceramics Doped with K4CuNb8O23

Sensitivity Characteristics of Acoustic Emission (AE) Sensor Using Thickness-Shear-Mode Piezoelectric Device

In this study, Acoustic Emission (AE) sensor was fabricated with the rectangular type Pb(Mg1/2W1/2)O3-Pb(Ni1/3Nb2/3)O3-Pb(Zr0.5Ti0.5)O3 (abbreviated as PMW-PNN-PZT) ceramic piezoelectric device using thickness shear mode. From the results of ATILA simulation, the specimen with the size of 8 × 6 × 8 mm3 was determined as the experimental piezoelectric device which shows the excellent thickness shear mode. Electromechanical coupling factor kp, piezoelectric constant d33 and g33 of PMW-PNN-PZT ceramics showed the excellent values of 0.63, 573 [pC/N], and 29.81 [10−3V·m/N], respectively, suitable for AE sensor device application. Thickness shear mode electromechanical coupling factor k15 was 0.61 at the specimen with the size of 8 × 6 × 8 mm3. The peak sensitivity of AE sensor using this thickness–shear-mode piezoelectric device showed 79 [dB] at 29.4 [kHz].

Driving of 35W(T5) fluorescent lamp by the electronic ballast using piezoelectric transformer

Recently, 40 W fluorescent lamps with 32 mm tube diameter are replaced with 32 W one with 26 mm in diameter to conserve lamp materials and to increase luminance efficiency. Moreover, 35, 28 and 14 W fluorescent lamps with 16 mm in diameter (T5), which are nowadays developed, also may replace 32 W lamps again. Application of slim lamps, however, requires small sized electronic ballast to fulfill the design philosophy of miniaturizing. However, the traditional magnetic ballasts operated at 50-60 Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight In this study, in order to solve these problems, a new type of electronic ballast which is composed of rectifier, active power corrector, series resonant half bridge inverter and piezoelectric transformer was proposed for driving T5 fluorescent lamp. Contour vibration mode piezoelectric transformer with ring/dot electrode structure was fabricated to the size of 27/spl times/27/spl times/2.5 mm/sup 3/ by cold isostatic pressing. Driving of piezoelectric transformer was carried out with input region for the ring electrode and output region for the dot electrode. A 35 W (T5) fluorescent lamp was successfully driven by the fabricated ballast with piezoelectric transformer. After driving the lamp for 25 min using the proposed electronic ballast, input power factor of 0.95, efficiency of 90.7%, were shown, respectively, at operating frequency of 79 kHz. And also, output power, efficiency and temperature rise of the piezoelectric transformer, 37.53 W, 92% and 25/spl deg/C, respectively.

Resonant Displacement and Piezoelectric Properties of Thickness Shear Mode Piezoelectric Devices According to Length/Thickness Ratio

In this study, thickness shear mode piezoelectric devices for AE sensor with excellent displacement and sensitivity characteristics were simulated using ATILA FEM program, and then fabricated. Displacement and electro mechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electromechanical coupling factor was obtained when the ratio of Length/Thickness was 1. The piezoelectric device of L/T

Dielectric and Piezoelectric Properties of (Na 0.5 K 0.5 ) 0.97 NbO 3 Ceramics Substituted with CeMnO 3

In this study, non-stoichiometric 1-x[(K0.5Na0.5)0.97(Nb0.96Sb0.04)O3] + x CeMnO3 + 0.8 mol%CuO + 0.2 wt% Ag2O (x=0, 0.005) ceramics were prepared by a conventional mixed oxide and carbonate method, their dielectric and piezoelectric properties were investigated with the variations of sintering temperature. As CeMnO3 substitution incereased, the density, piezoelectric constant(d33) and dielectric constant(er) were increased and the mechanical quality factor(Qm) was decreased. At the sintering temperature of 1100°C, the density, electromechanical coupling factor(kp), dielectric constant(er) and piezoelectric constant(d33) of 0.5mol% CeMnO3 specimen showed the optimun values of 4.475 g/cm3, 0.437, 552 and 166 pC/N, respectively. However, the mechanical quality factor(Qm) showed the minimum value of 380.

Effect of K 4 CuNb 8 O 23 and La 2 O 3 co-doping on the piezoelectric and dielectric properties of (K 0.5 Na 0.5 )(Nb 0.96 Sb 0.04 )O 3 ceramics

In this study, (K<inf>0.5</inf>Na<inf>0.5</inf>)−(Nb<inf>0.94</inf>Sb<inf>0.04</inf>)O<inf>3</inf> + 1.2mol% K<inf>4</inf>CuNb<inf>8</inf>O<inf>23</inf> + xmol%La<inf>2</inf>O<inf>3</inf> ceramics was prepared by conventional solid-state sintering method. The effect of La<inf>2</inf>O<inf>3</inf> on the crystal structure, dielectric and piezoelectric properties of the ceramics were investigated in order to improve the electrical and piezoelectric properties of lead-free piezoelectric ceramics. The density and the dielectric constant increased with increasing the amount of La<inf>2</inf>O<inf>3</inf> content. So, Electromechanical coupling factor (kp) and piezoelectric constant (d<inf>33</inf>) of the ceramics were considerably improved. At the 0.2mol% La<inf>2</inf>O<inf>3</inf> added composition ceramics sintered at 1080ଌ, kp, d<inf>33</inf> and g<inf>33</inf> showed optimum values of 0.38, 160pC/N and 37.4[10⁻³V·m/N], respectively.

Dielectric and piezoelectric properties of (K 0.5 Na 0.5 )(Nb 0.97 Sb 0.03 )O 3 ceramics according to the K 2 CuNb 8 O 23 addition

In this study, (K<inf>0.5</inf>N<inf>0.5</inf>)<inf>0.97</inf>(Nb<inf>0.97</inf>Sb<inf>0.03</inf>)O<inf>3</inf> +0.9 mol% K<inf>5.4</inf>Cu<inf>1.3</inf>Ta<inf>10</inf>O<inf>29</inf> + x mol% K<inf>2</inf>CuNb<inf>8</inf>O<inf>23</inf> (x = 0, 0.2, 0.6, 0.8) ceramics were prepared by a conventional mixed oxide method and their microstructure and electric properties were investigated. Secondary phase such as K<inf>6</inf>Ta<inf>10.8</inf>O<inf>30</inf> was made by the virtue of K<inf>2</inf>CuNb<inf>8</inf>O<inf>23</inf> addition in the (K<inf>0.5</inf>N<inf>0.5</inf>)<inf>0.97</inf>(Nb<inf>0.97</inf>Sb<inf>0.03</inf>)O<inf>3</inf> system ceramics. However, the sinterability of the ceramics increased with increasing K<inf>2</inf>CuNb<inf>8</inf>O<inf>23</inf> content. At the 0.6mol% K<inf>2</inf>CuNb<inf>8</inf>O<inf>23</inf> added composition ceramics sintered at 1060°C, kp and d<inf>33</inf> showed the optimum values of 0.39 and 145[pC/N, respectively, suitable for piezoelectric actuator application.

Piezoelectric and Dielectric Characteristics of Low Loss Low Temperature Sintering PMN-PNN-PZT Ceramics with the amount of PNN Substitution

In this study, in order to develop low temperature sintering ceramics for multilayer piezoelectric actuator, ceramics system were fabricated using sintering aids and the specimens were sintered at . Thereafter, their piezoelectric and dielectric characteristics were investigated according to the amount of PNN substitution. At 9 mol% PNN substitution, density, electromechanical coupling factor (), dielectric constant, mechanical quality factor () and piezoelectric constant () showed the optimum value of , 0.60, 1640, 1323 and 387 pC/N, respectively. It is considered that these values are suitable for piezoelectric divece application such ad multilayer piezoelectric actuator and ultrasonic vibrator with pure Ag internal electrode.

Piezoelectric Properties of Low Loss and Low Temperature sintering PMN-PNN-PZT Ceramics According to the Amount of MnO 2 Addition

In this study, in order to develop the composition ceramics for low loss and low temperature sintering multilayer piezoelectric actuator, PMN-PNN-PZT ceramics were fabricated using Li₂CO₃ and Na₂CO₃ as sintering aids, and their piezoelectric and dielectric characteristics were investigated according to the amount of MnO₂ addition. At the sintering temperature of 900 , density and mechanical quality factor (Q_m) of specimen showed maximum value of 7.81[g/cm³], 1186 at 0.2wt% MnO₂, electromechanical coupling factor (k_p), piezoelectric constant (d₃₃) of specimen showed the maximum value of 0.608, 377[pC/N] at 0.1 wt% MnO₂ and dielectric constant (epsiv_r) slightly decreased with increasing MnO₂. At the composition ceramics sintered at 900 C with 0.2 wt% MnO₂, density, electromechanical coupling factor (k_p), mechanical quality factor (Q_m), dielectric constant (epsiv_r) and piezoelectric constant (d₃₃) showed the optimum value of 7.81[g/cm³], 0.597, 1186, 919, 356[pC/N], respectively, for multilayer piezoelectric actuator application.