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Detailed Program
Paper Number : LP-I06
Time Frame : 11:10~11:35
Presentation Date : Friday, 28, November
Session Name : Leadfree Piezoelectrics
Session Chair 1# : Wook Jo
Session Chair 2# : Wataru Sakamoto
Piezoelectric Properties Of (Bi0.5Na0.5)TiO3-BaTiO3-Based Lead-Free Ceramics And Its Application To Ultrasonic Cleaner
Tonshaku TOU
Honda Electronics Co., Ltd.
Keywords: Lead-free, Piezoelectricity, Transducer, Cleaner, Piezoceramics

Pb(Zr,Ti)O3 piezoceramics has been widely used in actuators, sensors, resonators and ultrasonic transducers. However, environmentally friendly piezoelectric materials are required to replace the materials due to the toxicity of lead oxide. (Bi0.5Na0.5)TiO3-based ceramics is considered to be a good candidate for lead-free ceramics. We have developed a new lead-free piezoceramics (Bi0.5Na0.5)TiO3-BaTiO3-(Bi0.5Na0.5)(Mn1/3Nb2/3)O3. Here, the high power characteristics of the ceramics were reported. The properties of a bolt-clamped Langevin transducer (BLT) using the ceramics were investigated. The cleaning effect of an ultrasonic cleaner using the BLTs was evaluated. The problem of practical application and the solution was reported.

Commercially available Bi2O3, Na2CO3, BaCO3, TiO2, Nb2O5 and MnCO3 powders, all with a purity of at least 99.0% were used as raw materials. After the corresponding metal oxides of the prescribed amount being mixed by ball-milling, (Bi0.5Na0.5)TiO3-BaTiO3-(Bi0.5Na0.5)(Mn1/3Nb2/3)O3 was synthesized by heating at 850¡ÆC for 2 hours, and then pulverized. The pulverized powder was formed and sintered isothermally at 1100- 1200¡ÆC for 2 hours. The piezoelectric properties of the sample were measured after poled. The poled samples were used to fabricate BLT. The BLTs were applied to ultrasonic cleaner.

Various quantities of (Bi0.5Na0.5)(Mn1/3Nb2/3)O3 were added into (Bi0.5Na0.5)TiO3-BaTiO3 ceramics. Optimum composition 0.82(Bi0.5Na0.5)TiO3-0.15BaTiO3- 0.03(Bi0.5Na0.5)(Mn1/3Nb2/3)O3 ceramicsshows a good piezoelectric behavior of Kt=45%, Qm=500, d33=110 pC/N and high mechanical strength. Figure 1 shows the vibration velocity of the vibration surface of the BLT (28 kHz) as a function of input electric power. The vibration velocity of both BLTs increased with an increase in input electric power. The vibration velocity of BLT using lead-free piezoelectric ceramics was larger than that of hard PZT at the same input power. This suggests that the power loss in lead-free BLT is smaller than that in hard BLT. Figure 2 variation of the intensity of ultrasound of the cleaner (15 BLTs, 600W type) with distance from the bottom. The intensity of ultrasound of cleaner using lead-free ceramics was higher than that of hard PZT. This result was correspondent to the relationship between vibration velocity and input electric power as shown in Fig. 1. Therefore, the ultrasonic cleaner using lead-free ceramics had a high clean effect which was good for commercial application.
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