Disk-type piezoelectric transformer of a Na0.5K0.5NbO3–CuNb2O6 lead-free ceramic for driving T5 fluorescent lamp

Lead-free (Na0.5K0.5)NbO3 (NKN) ceramics doped with 1 mol% CuNb2O6 (CN) ceramics were prepared using the conventional mixed oxide method, with a sintering temperature of 1075 °C. Microstructural analyses of the NKN–01CN ceramics were carried out and compared, using X-ray diffraction (XRD). NKN–01CN ceramics sintered at 1075 °C not only exhibited excellent ‘hard’ piezoelectric properties of kp = 40%, kt = 45%, k33 = 57%, a ferroelectric property of Ec = 23 kV/cm, and an extraordinarily high mechanical quality factor (Qm) of 1933 but also showed excellent stability with temperature (TCF = −154 ppm/°C). The piezoelectric transformer was simplified, using an equivalent circuit, and analyzed, using MATLAB; the simulation data agreed well with the experimental results. An efficiency of 95.7% was achieved for the NKN–01CN piezoelectric transformer with load resistance of 20 kΩ. An 8 W T5 fluorescent lamp was successfully driven by the NKN–01CN piezoelectric transformer.

► CuNb2O6 dopants were doped into NKN ceramics not only improved the density but also exhibited superior piezoelectric characteristic, temperature stability of resonance frequency.
► Lead-free NKN-01CN piezoelectric transformer was simplified as an equivalent circuit and analyzed using MATLAB.
► An 8W T5 fluorescent lamp was successfully driven by the NKN-01CN piezoelectric transformer.