Hyun-Sang Yoon

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

Piezoelectric properties of PNW-PMN-PZT ceramics for high power piezoelectric transformer

Piezoelectric properties of Pb/sub 1-a/Sr/sub a/(Ni/sub 1/2/W/sub 1/2/)/sub 0.02/(Mn/sub 1/3/Nb/sub 2/3/)/sub b/(Kr/sub x/, Ti/sub y/)/sub 1-0.02-b/O/sub 3/ ceramics added to 0.5 wt% PbO, 0.3 wt%Fe/sub 2/O/sub 3/ and 0.25 wt% CeO/sub 2/ were investigated with the variations of a=0-0.06, b=0.05-0.07, x=0.49-0.51, and y=0.49-0.51. Mechanical quality factor, coercive field and Curie temperature with the decrease of Zr/Ti ratio were increased by the increase of tetragonality. According to the increase of PMN mol%, grain size decreased and coercive field increased. Moreover, dielectric constant and mechanical quality factor increased and Curie temperature and coercive field decreased with the increase of the substitution of Sr mol% to Pb sites. Taking into consideration the dielectric constant of 1,680, mechanical quality factor of 1,814, and temperature stability of resonant frequency of TCfr 88 at a=0.06, b=0.07, x=0.51, and y=0.49 composition ceramics, it can be concluded that this composition is the best one for piezoelectric transformer.

Electrical and Frequency Characteristics of Third-Overtone Vibration-Mode Surface Mount Device High-Frequency Filter Using Modified PbTiO3 Ceramics

In this study, a 3rd-overtone thickness-vibration-mode surface mount device (SMD) filter was manufactured using modified PbTiO3 system ceramics for application as an intermediate frequency (IF) filter with a split electrode and gap size. To investigate the effects of the split electrode and gap size on the filter characteristics of the 3rd-overtone-mode energy-trapped filter, ceramic wafers were fabricated by etching split rectangular electrodes with sizes (b ×d) of b=0.4, 0.6, 0.8 and 1 mm, d=0.3, 0.4, 0.5 and 0.6 mm and gap sizes (c) of the c=0.2, 0.3, 0.4 and 0.6 mm, respectively. Then, SMD ceramic filters were fabricated with the size of 3.7 ×3.1 mm2. SMD ceramic filter with the size of b=0.8 mm, d=0.4 mm and c=0.4 mm showed insertion loss of 2.951 dB, 3 dB bandwidth of 54.7 kHz and 20 dB stop bandwidth of 129.27 kHz. Also, these two filters were cascaded and their bandwidth characteristics were investigated by varying the coupling capacitance to check their applicability as high frequency band-pass filters. The cascaded filter showed a higher stop band, reduction of spurious response and increase of selectivity. With increasing coupling capacitance, insertion loss increased but spurious response decreased. The cascaded filter with a coupling capacitance of 15 pF showed insertion loss of 5.643 dB, 3 dB bandwidth of 55.089 kHz and 20 dB bandwidth of 83.608 kHz.

Structural properties and effect of excess pb on pb(zr0.52ti0.48)o3 thin films prepared by sol-gel processing

Abstract Pb(Zr0.52Ti0.48)03 stock solution prepared by sol-gel processing was spin-coated on Pt/SiO2/Si substrates and annealed by RTA (Rapid Thermal Annealing). The crystal structure and the growth mechanism of the films were proposed based on the observation of crystallization process and microstructure of the films fabricated with different conditions, and the effects of excess Pb addition were studied. Films were crystallized into rhombohedral structure by annealing at 550°C for 60 sec or 600°C for 20 sec. The grain size of the film increased as the annealing temperature increases and the films were grown into columnar structure perpendicular to the substrate. The degradation of electrical properties due to Pb loss during RTA annealing was observed, and the addition of 10 wt% of excess Pb to the stock solution could compensated the Pb loss.

Electrical Properties of Step-down Multilayer Piezoelectric Transformer for AC-DC converter

Multilayer piezoelectric transformers (MPT) were manufactured using PZN-PMN-PZT ceramics and their electrical properties were then investigated according to frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value in the vicinity of 73 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the piezoelectric transformer showed the temperature rise of about 21degC at the output power of 15 W. The multilayer piezoelectric transformer manufactured at low cofiring temperature of ~940degC using PZN-PMN-PZT ceramics could be stably driven as the step-up or down transformers.

Electrical Properties of (Pb, La, Nd)(Mn, Sb, Ti)O3 System Ceramics for 20 MHz Ceramic Resonators

The electrical and resonance characteristics of energy-trapped 20 MHz SMD-type resonators using the 3rd overtone thickness vibration mode were investigated as a function of internal electrode diameter. With increasing electrode diameter, resonant resistance in the 3rd overtone mode decreased and electromechanical coupling factor (kt3) in the 3rd overtone mode showed constant values. Taking into consideration the mechanical quality factor (Qmt3) of 5,552 and dynamic range (D.R.) of 60.72 dB in the 3rd overtone mode, the ceramic resonator with the electrode diameter of 1.13 mm was found to be suitable for 20 MHz resonator application.

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.

Electrical Properties of High Power Step Down Multilayer Piezoelectric Transformer using Low Temperature Sintering PMN-PNN-PZT Ceramics

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.

PIEZOELECTRIC AND DIELECTRIC PROPERTIES OF LOW TEMPERATURE SINTERING PMN-PZN-PZT CERAMICS ACCORDING TO THE AMOUNT OF PbO

ABSTRACT In this study, in order to develop the composition ceramics for low loss multilayer piezoelectric actuator, Pb x [(Mn1/3Nb2/3)0.07(Zn1/3Nb2/3)0.06(Zr0.48Ti0.52)0.87]O3(abbreviated as PMN-PZN-PZT) ceramics were fabricated according to the amount of PbO, using two-stage calcinations method and conventional mixed oxide process. And also, their dielectric and piezoelectric properties were investigated. Excess PbO improved all the dielectric and piezoelectric characteristics due to the enhancement of sinterability. At the PbO of 1.00 mol and sintering temperature of 930°, the properties of specimen showed the optimum values of density = 7.79 g/cm3, εr = 1274, kp = 0.553, Qm = 1576, d33 = 318 pC/N, respectively for low loss multilayer piezoelectric actuator application.

Effects of Li/sub 2/CO/sub 3/ and Bi/sub 2/O/sub 3/ additives on sintering temperature and piezoelectric properties of PNIN-PCW-PZT ceramics for multilayer piezoelectric transformer

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics doped with Li/sub 2/CO/sub 3/, Bi/sub 2/O/sub 3/ and CuO as sintering aids were manufactured, and their microstructural, dielectric and piezoelectric properties were investigated. When the only CuO was added, specimens could not be sintered below 980/spl deg/C. However, when Li/sub 2/CO/sub 3/ and Bi/sub 2/O/sub 3/ were added, specimens could be sintered below 980/spl deg/C. Li/sub 2/CO/sub 3/ and Bi/sub 2/O/sub 3/ addition were proved to lower sintering temperature of piezoelectric ceramics due to the effect of Li/sub 2/O-Bi/sub 2/O/sub 3/ liquid phase. Li/sub 2/CO/sub 3/ and Bi/sub 2/O/sub 3/ added specimens showed higher piezoelectric properties than those of the only CuO added specimens. At 0.2wt% Li/sub 2/CO/sub 3/ and 0.3wt% Bi/sub 2/O/sub 3/ added specimen sintered at 920/spl deg/C, the dielectric constant (/spl epsi//sub r/) of 1457, electromechanical coupling factor (k/sub p/) of 0.56 and mechanical quality factor (Q/sub m/) of 1000 were shown, respectively. These values are suitable for multilayer piezoelectric transformer application.