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Lead-free piezoelectric ceramic (K0.5Na0.5)NbO3 with MnO2 and K5.4Cu1.3Ta10O29 doping for piezoelectric transformer application

In this study, K0.5Na0.5NbO3+0.25 mol% MnO2+0.38 mol% K5.4Cu1.3Ta10O29 lead-free piezoelectric ceramics were prepared by a conventional ceramic sintering technique and fabricated into a square-plate contour-vibration-mode piezoelectric transformer. The ceramic was well sintered to a dense structure at 1110 °C. Because of the pinning effects provided by the defect dipoles, the ceramic exhibited excellent ‘hard’ piezoelectric characteristics: d33 = 90 pC N−1, kp = 0.40, εr = 300, tanδ = 0.003 and Qm = 1900. The piezoelectric transformer showed a maximum power density of 10 W cm−3 with a temperature rise of 20 °C. When operated with a matching load of 8 kΩ, the maximum efficiency of the transformer reached 96%. The transformer has great potential to be used in power supply units and other electronic circuits.