Effects of improved process for CuO-doped NKN lead-free ceramics on high-power piezoelectric transformers.

Research paper by Song-Ling SL Yang, Cheng-Che CC Tsai, Yi-Cheng YC Liou, Cheng-Shong CS Hong, Bing-Jing BJ Li, Sheng-Yuan SY Chu

Indexed on: 01 Dec '11Published on: 01 Dec '11Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control


In this paper, the effects of the electrical proper- ties of CuO-doped (Na(0.5)K(0.5))NbO(3) (NKN) ceramics prepared separately using the B-site oxide precursor method (BO method) and conventional mixed-oxide method (MO method) on high-power piezoelectric transformers (PTs) were investigated. The performances of PTs made with these two substrates were compared. Experimental results showed that the output power and temperature stability of PTs could be enhanced because of the lower resonant impedance of the ceramics prepared using the BO method. In addition, the output power of PTs was more affected by the resonant impedance than by the mechanical quality factor (Q(m)) of the ceramics. The PTs fabricated with ceramics prepared using the BO method showed a high efficiency of more than 94% and a maximum output power of 8.98 W (power density: 18.3 W/cm(3)) with temperature increase of 3°C under the optimum load resistance (5 kΩ) and an input voltage of 150 V(pp). This output power of the lead-free disk-type PTs is the best reported so far.