A Rosen-type piezoelectric transformer employing lead-free K0.5Na0.5NbO3 ceramics
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Lead-free K0.5Na0.5NbO3–K5.4Cu1.3Ta10O29–MnO2 (KNN–KCT–Mn) ceramics have been prepared by a conventional ceramic sintering technique. The ceramics show excellent piezoelectric properties for application in power devices, and the optimum properties measured are as follows: piezoelectric constant d 33 = 90 pC/N, planar electromechanical coupling factor k p = 0.40, mechanical quality factor Q m = 1900, remanent polarization P r = 11.8 μC/cm2, coercive field E c = 0.85 kV/mm. A Rosen-type piezoelectric transformer with a dimension of 21 mm × 6 mm × 1.2 mm was fabricated using the KNN–KCT–Mn ceramics. Properties of the piezoelectric transformer operating in the first and second modes have been characterized. For the first mode, the transformer has a maximum output power of 0.7 W with a temperature rise of 14 °C. For the second mode, the maximum output power of the transformer is 1.8 W with a temperature rise of 33 °C. KNN–KCT–Mn ceramics have shown to be a potential lead-free candidate to be used in high-voltage–low-current devices.
KeywordsLoad Resistance Maximum Output Power Voltage Gain Electromechanical Coupling Factor Mechanical Quality Factor
This work was supported by the Niche Area Project (No. 1-BB95) and the Centre for Smart Materials of The Hong Kong Polytechnic University.
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