Kwanghyun Chung

Piezoelectric and Dielectric Properties of (LiNaK)(NbTaSb)O3 Ceramics with Variation in Poling Temperature

In this study, lead-free (LiNaK)(NbTaSb)O3 piezoelectric ceramics were fabricated on the basis of the amount of K2CO3 addition, and their piezoelectric and dielectric properties were investigated by varying the amount of K2CO3 addition and poling temperature. First, to achieve optimum poling conditions for manufactured specimens, the poling temperature was varied to be 0, 20, 50, 80, and 110 °C. The optimum poling temperature was 20 °C. It was found that 0.1 wt % K2CO3-added (Li0.04Na0.44K0.52) (Nb0.86Ta0.1Sb0.04)O3 ceramics exhibit excellent piezoelectric properties in an experiment performed on the basis of the amount of K2CO3 addition. That is, a 0.1 wt % K2CO3-added specimen showed a large electromechanical coupling factor kp=0.494, a large piezoelectric constant d33=274 pC/N, and a high density of 4.65 g/cm3 at the poling temperature of 20 °C.

Dielectric and Piezoelectric Properties of Low-Temperature-Sintering Pb(Mg1/2W1/2)O3-Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3 Ceramics for Multilayer Piezoelectric Actuator

In this study, in order to develop low-temperature-sintering ceramics for a multilayer piezoelectric actuator, Pb(Mg1/2W1/2)O3-Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMW-PNN-PZT) ceramics were fabricated using Li2CO3 and CaCO3 as sintering aids and their dielectric and piezoelectric properties were investigated in relation to the amount of Bi substitution. Piezoelectric actuators require both a high piezoelectric constant (d33) and a high electromechanical coupling factor (kp). Accordingly, in this study, Bi was substituted at the Pb site of basic composition PMW-PNN-PZT ceramics for the enhancement of kp and d33. With increasing Bi substitution, density gradually increased. At the sintering temperature of 900°C, the electromechanical coupling factor (kp) and piezoelectric constant (d33) of PMW-PNN-PZT composition ceramics with 1.0 mol % Bi substitution as well as 0.2 wt % Li2CO3 and 0.25 wt % CaCO3 showed the optimal value of 0.618 and 473 pC/N, respectively, for multilayer piezoelectric actuator application.

THE LOW TEMPERATURE SINTERING PROPERTIES OF MODIFIED PbTiO3 CERAMICS

ABSTRACT In the study, in order to develop low-temperature-sintering ceramics for multilayer piezoelectric transformer, (Pb0.76Ca0.24 −xSrx)Ti0.96 (Mn1/3Sb2/3)0.04O3 ceramics were fabricated using Na2CO3 and Li2CO3 as sintering aids and their dielectric and piezoelectric properties were investigated with amount of Sr substitution. The modified PbTiO3 ceramics with a composition of (Pb0.76Ca0.24 − xSrx)Ti0.96 (Mn1/3Sb2/3)0.04O3; x = 0 − 0.05 were prepared by conventional mixed-oxide at sintering temperature of 880, 900 and 930°C. At the sintering temperature of 900°C, thickness vibration mode electromechanical coupling factor (Kt) and thickness vibration mode mechanical quality factor (Qmt) of composition ceramics with 1.0mol% Sr substitution showed the optimal value of 0.50 and 1575 respectively, for multilayer piezoelectric transformer application.

Dependence of Annealing Temperature on Properties of PZT Thin Film Deposited onto SGGG Substrate

thin films of thickness were grown on substrate by RF magnetron sputtering at annealing temperatures ranging from to . We evaluated the residual stress, by using a William-Hall plot, as a function of the annealing temperatures of PZT thin film with a constant thickness. As a result, the residual stresses of PZT thin film of thickness were changed by varying the annealing temperature. Also, we measured the hysteresis characteristic of PZT thin films of thickness to evaluate for application of an optoelectronic device.

Effect of Particle Size on the Dielectric and Piezoelectric Properties of 0.95(K 0.5 Na 0.5 )NbO 3 -0.05BaTiO 3 Lead-free Piezoelectric Ceramics

The particle sizes of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 powder were controlled by secondary milling time after calcination. The average particle sizes, Dmean, of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 powders were critically changed from 14.31 μm to 0.91 μm by secondary milling time. The dielectric and piezoelectric properties of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 ceramics depended on the particle sizes of powders after calcination and the secondary milling process. As secondary milling times after calcination were increased to more than 48 hr, the dielectric and piezoelectric properties of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 ceramics were deteriorated.

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.

Piezoelectric and Dielectric Characteristics of Low Temperature Sintering Pb(Mg 1/2 W 1/2 )O 3 -Pb(Mn 1/3 Nb 2/3 )O 3 -Pb(Zr 1/2 Ti 1/2 )O 3 Ceramics with the Substitution of Pb(Mg 1/2 W 1/2 )O 3

In this study, in order to develop low temperature sintering piezoelectric ceramics for LTCC (low-temperature co-fired ceramic) multilayer piezoelectric actuator, PMW-PMN-PZT ceramics using 0.2 wt% Li2CO3 and 0.25 wt% CaCO3 as sintering aids were investigated according to the variation of PMW substitution. The composition ceramics could be sintered at 900degC by adding sintering aids. As the amount of PMW substitution increased, the crystalline structure of PMW-PMN-PZT ceramics moved gradually from tetragonal phase to rhombohedral phase, and MPB (morphotrophic phase boundary) region appeared at 2 mol% PMW substitution. At the sintering temperature of 900degC, the density, electromechanical coupling factor (kp), mechanical quality factor (Qm), dielectric constant (epsivtau), piezoelectric constant (d33) and Curie temperature (Tc) of 2 mol% PMW substituted PMW-PMN-PZT ceramics showed the optimal values of 7.88 g/cm3, 0.58, 1002, 1264, 352 pC/N and 336degC, respectively, for LTCC multilayer piezoelectric actuator application.

Electrical Characteristics of Piezoelectric Transformer using Low Temperature Sintering PCW-PMN-PZT Ceramics

In this study, piezoelectric transformer was manufactured at the sintering temperature of , and then the feasibility of application to low temperature sintering piezoelectric transformers was investigated by evaluating the electrical characteristics of it. The voltage ratio of piezoelectric transformer showed the maximum value at the resonant frequency of input part, and increased according to the increase of load resistance. The output power and efficiency of piezoelectric transformer showed the superior properties when the output impedance of it coincides with the load resistance. Piezoelectric transformer manufactured at the low temperature of showed the heat generation less than at the output power of 30 W, and stable driving characteristics.

Dielectric and Piezoelectric Properties of Low Temperature Sintering PCW-PMN-PZT Ceramics according to MnO 2 Addition

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics using LiCO, BiO, and CuO as sintering aids were manufactured according to the amount of MnO addition. Their microstructural, dielectric and piezoelectric properties were investigated. When the sintering aids were added, specimens could be sintered below 95, but mechanical qualify factor decreased. Therefore, MnO was added excessively to the PCW-PMN-PZT ceramics to increase mechanical quality factor. At the sintering temperature of 95, the density, dielectric constant(), electromechanical coupling factor(k), mechanical quality factor(Q) and Curie temperature(T) of 0.1 wt% MnO added specimen showed the optimal values of 7.75 g/㎤, 1503, 0.57, 1502, and 337, respectively, for multilayer piezoelectric transformer application.ation.n.

Piezoelectric and Dielectric Characteristics of Low Temperature Sintering PNW-PMN-PZT Ceramics according to CaCO 3 Addition

In this study, in order to develop low temperature sintering ceramics for ultrasonic vibrator application, PNW-PMN-PZT system ceramics were manufactured according to the amount of CaCO addition, and their piezoelectric, dielectric and microstructural characteristics were investigated. The ceramic specimens could be sintered at sintering temperature below 1000 due to the effect of LiCO-CaCO liquid phase produced by the reaction of LiCO and CaCO. At 0.2 wt% LiCO and 0.25 wt％ CaCO added specimen sintered at 920 , the density, electromechanical coupling factor(k), mechanical quality factor(Q) and dielectric constant showed the optimal value of 7.78 g/㎤, 0.49, 1396, and 1300, respectively, for ultrasonic vibrator application.ion.