Lead-free piezoelectric ceramic (K0.5Na0.5)NbO3with MnO2and K5.4Cu1.3Ta10O29doping for piezoelectric transformer application

In this study, K 0.5 Na 0.5 NbO 3 +0.25 mol% MnO 2 +0.38 mol% K 5.4 Cu 1.3 Ta 10 O 29 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: d 33 = 90 pC N −1 , k p = 0.40, ε r = 300, tanδ = 0.003 and Q m = 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.