In this study, Pb(Ni_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃ ceramics substituted with Pb(Mg_1/2W_1/2)O₃ were fabricated with the variation of CuO for application to ultrasonic cleaning of removable orthodontic appliances (ROA). And their piezoelectric and dielectric properties were investigated. At the 0.12 wt% CuO added ceramics sintered at 930℃, the excellent values of dielectric constant=2,519, density=7.82 g/㎤, kp=0.64, d₃₃=536 pC/N, Qm=57 were obtained, respectively. These values were suitable for application to ultrasonic cleaning of ROA.

In a Pb-included piezoelectric composition, Sr_yPb_1-y[(Zn_1/3Nb_2/3)_x-(Ni_1/3Nb_2/3)_0.2-(Zr_0.46Ti_0.54)_0.8-x]O₃ was selected in order to attain high piezoelectric properties. According to the PZN ratio (x) and the amount of Sr doping (y), the crystal structure, microstructure and piezoelectric properties were measured and evaluated. In the case of Sr 4 mol% doping, the piezoelectric properties were the highest for a PZN ratio of 0.1. In this condition, the grain size was larger and the intensity was higher. With the PZN ratio fixed and varying the Sr doping, the piezoelectric properties increased until 10 mol% doping and then decreased for over 12 mol% doping. In the case of x＝0.1 and y＝10 mol%, the best piezoelectric properties were obtained, i.e., d₃₃＝660 pC/N and k_p＝68.5%, and these values seem to be related to the grain size and crystal structure.

Pb(Zr, Ti)O₃ (PZT) is a piezoelectric material applied in a typical actuator and has been actively studied. However, in order to overcome the limitations of PZT, piezoelectric ceramics comprising mixed solid solutions of PZT with various relaxer electric materials have been studied. The Pb(Zn_1/3Nb_2/3)-Pb(Ni_1/3Nb_2/3)-Pb(Zr, Ti)O₃ (PZN-PNN-PZT) piezoelectric ceramic, known to have high piezoelectric constant and electromechanical coupling coefficient, was studied herein. The piezoelectric characteristics with various Zr contents (Zr/Ti ratios), PZN molar ratios, and sintering temperatures were compared. The piezoelectric properties of d₃₃＝580 pC/N and kP＝0.68 were obtained with the 0.1PZN-0.2PNN-0.7PbZr_0.46Ti_0.54O₃ composition sintered at 1,290℃.

Pb(Mn_1/3Nb_2/3)_0.07(Ni_1/3Nb_2/3)_0.10(Zr_0.5Ti_0.5)_0.83O₃ composition ceramics with high piezoelectric properties were fabricated by the columbite precursor method for ultrasonic generators, and the effects of sintering temperature on microstructure and piezoelectric properties were systematically investigated. It was found that the tetragonality of the ceramics decreased with increase in sintering temperature. Moreover, excellent physical properties such as d₃₃=447 pC/N, ε_r=1,843, k_p=0.641, and Q_m=1,207 were obtained for an ultrasonic generator when the second calcination temperature and sintering temperature were 720℃ and 920℃, respectively.

In this paper, Pb(Mn_1/3Nb_2/3)_0.07(Ni_1/3Nb_2/3)_0.10(Zr_0.5Ti_0.5)_0.83O₃ ceramics were fabricated by the conventional solid state method to obtain excellent dielectric properties for ultrasonic generators. The effects of 2nd calcination temperature on their microstructure and piezoelectric properties were systematically investigated. The tetragonality increased in the ceramics when 2nd calcination temperature increased to the optimized temperature at 750℃. At that temperature, excellent physical properties (d₃₃= 352 pC/N, ε_r= 1,687, k_p= 0.570, Q_m= 1,640) were obtained for ultrasonic generator application.

In this study, in order to develop the composition ceramics for ultrasonic sensor with high d33*g33, (Pb1-3x/2Bix(Mg1/2W1/2)0.03(Ni1/3Nb2/3)0.09(Zr0.5Ti0.5)0.88O3)(PMW-PNN-PZT) system ceramics were prepared using CuO as sintering aids. And then, their microstructure, piezoelectric and dielectric characteristics were systemetically investigated with bismuth substitution. The PMW-PNN-PZT ceramic specimens could be sintered at sintering temperature of 940℃ by adding sintering aids. At x=0.015 specimen, the density, electromechanical coupling factor(kp), dielectric constant, piezoelectric constant(d33) and piezoelectric figure of merit(d33*g33) indicated the optimal properties of 7.90 g/cm3, 0.67, 2,511, 628 pC/N, and 17.7 pm2/N, respectively, for duplex ultrasonic sensor application.

In this work, [Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)x(Zr0.5Ti0.5)0.97-xO3-BiFeO3] (x=0.02 to 0.12) composition ceramics were fabricated by the conventional soild state reaction method and their microstructure and piezoelectric properties were investigated according to PNN substitution. The addition of small amount of BiFeO3, Li2CO3, and CaCO3 were used in order to decrease the sintering temperature of the ceramics. The XRD (x-ray diffraction patterns) of all ceramics exhibited a perovskite structure. The sinterability of PMW-PNN-PZT-BF ceramics was remarkably improved using liquid phase sintering of CaCO3, Li2CO3. However, it was identified from of the X-ray diffraction patterns that the secondary phase formed in grain boundaries decreased the piezoelectric properties. According to the substitution of PNN, the crystal structure of ceramics is transformed gradually from a tetragonal to rhombohedral phase. The x=0.10 mol PNN-substituted PMW-PNN-PZT-BF ceramics sintered at 920 showed the optimum values of piezoelectric constant(d33), piezoelectric figure of merit(d33·g33), planar piezoelectric coupling coefficient(kp) and density : d33=566 [pC/N], g33=29.28 [10-3mV/N], d33·g33=16.57 [pm2/N], kp=0.61, density=7.82 [g/cm3], suitable forduplex ultrasonic sensor application.

In this paper, in order to develop the composition ceramics with the outstanding piezoelectric properties, (Mg_{1/2} W _{1/2} )_{0.03} (OWNS_{1/3} Nb_{2/3})_{0.09} (Zr_{0.5} Ti_{0.5})_{0.88} O_{3} ceramics substituted with BiFeO_{3} were prepared by the conventional solid-state reaction method. The addition of small amount of Li2CO_{3} and CaCO_{3} as sintering aids decreased the sintering temperature of the ceramics. The effects of BiFeO3 substitution on their piezoelectric and dielectric properties were investigated. when 0.015 mol BiFeO_{3} was substituted, the optimal physical properties of d33=590 pC/N, Ec=8.78 kV/mm were obtained.

In this study, (1-x)Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)0.09(Zr0.5Ti0.5)0.88O3 + xCeMnO3 (x= 0∼0.02) ceramics were prepared by Columbite precursor method. The phase structure, ferroelectric and piezoelectric properties were systematically investigated. It was found that PMW-PNN-PZT possessed superior electrical properties due to its composition close to the MPB (morphotropic phase boundary). Coercive electric field of 10.05 [kV/cm] and density of 7.88 [g/cm3] were obtained when the substitution amount of CeMnO3 is x=0.02. In contrast, specimens with x=0.01 showed the mechanical quality factor(Qm) of 1,091 and the electromechanical coupling factor(kp) of 0.613.

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)0.09(Zr0.5Ti0.5)0.88O3 ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties (d33= 422pC/N, d31= 161 pC/N, εr= 1,905, kp= 0.55, Qm= 160) were obtained.