Chinese University Boosts Piezoelectric Effect of ZnO

Mar 31, 2012
Tetsuo Nozawa, Nikkei Electronics
The hysteresis curve of the piezoelectric effect of the ZnO containing V. The black line indicates displacement determined by applied voltage, and the blue line represents electric charge per unit stress.  (c) Science  China Press
The hysteresis curve of the piezoelectric effect of the ZnO containing V. The black line indicates displacement determined by applied voltage, and the blue line represents electric charge per unit stress. (c) Science China Press
[Click to enlarge image]

A research group at Tsinghua University in China announced that it has used zinc oxide (ZnO) foil and achieved a piezoelectric effect as large as that of lead zirconate titanate (PZT).

The achievement was announced in a thesis published in SCIENCE CHINA Technological Sciences, a Chinese academic journal.

Piezoelectric effect is a phenomenon where an electromotive force is generated by applying stress to a material. It is used for various pressure sensors including touch panels and a variety of devices such as actuators and SAW (surface acoustic wave) devices.

Thus far, PZT has been mainly used as a piezoelectric material having piezoelectric effect despite concern for the lead contained in it. If PZT can be replaced with ZnO, which does not contain lead and is more environmentally friendly, the piezoelectric material will possibly be used for a wider variety of applications.

Piezoelectric effect drastically improved by adding vanadium

The research group achieved a d33 value of about 170pC/N with Zn0.975V0.025O, a material made by adding vanadium (V) to a ZnO foil. d33 is one of the indicators of the strength of piezoelectric effect.

The d33 of PZT is 400-2,200pC/N, which is higher than that of the new ZnO material containing V. However, according to the thesis, the piezoelectric effect of ZnO that does not contain V is 9.9-12.4pC/N. Therefore, the group drastically improved the piezoelectric effect of ZnO this time.