EFFECT OF SURFACE ACOUSTIC-WAVE PROPAGATED ON FERROELECTRIC LINBO3 ON CATALYTIC ACTIVITY OF A DEPOSITED PD THIN-FILM

The effect of a surface acoustic wave (SAW) generated on a LiNbO3 ferroelectric crystal on the catalytic activity of a Pd thin film deposited on SAW propagation path was studied. The catalytic activity for ethanol oxidation immediately increased and became several times larger than the activity before the SAW was turned on. With the SAW off, the activity decreased to the original level. The activation energy of the reaction decreased from 42 to 29 kJ mol-1 with the SAW on. A half reaction order in the oxygen pressure and the first order in ethanol pressure were obtained, both of which remained nearly unchanged with the SAW on. It is proposed that the SAW gives rise to a decrease in the true activation energy. For an electroluminescent Cu-doped ZnS layer deposited instead of the catalyst, a pulsed SAW caused acoustoluminescence, the intensity of which increased with increasing SAW power. It was shown that an electric field as high as 10(4) V cm-1 was generated on the SAW propagating surface. The SAW effect on the catalytic activity was discussed on the basis of the electric field and geometric effects.