ANALYSIS OF ULTRASONIC VELOCITY-MEASUREMENTS ON SINTERING ZINC-OXIDE

A technique is presented for accurate measurement of the longitudinal wave velocity up to 1050 degrees C in sintering powder compacts. The t echnique uses laser generation and contact detection of the ultrasonic signal. Representative results are presented for heating cycles perfo rmed upon sintering ZnO powder compacts, and upon a pre-sintered dense ZnO sample. The data demonstrate the capability for performing in-sit u longitudinal wave velocity measurements at high temperatures, and in attenuative materials such as sintering ceramic powder compacts. In a ddition, the data demonstrate the sensitivity of ultrasonic velocity m easurements to changes within the sintering compact which are not dete ctable by dimension measurement alone. A novel application of ultrason ic velocity measurements performed in-situ on sintering ZnO is present ed. This application is based upon interpretation of longitudinal wave velocity measurements in the context of existing models treating surf ace area reduction during sintering. A previously observed correlation between the longitudinal wave ultrasonic velocity and the specific su rface area facilitates this interpretation. The analysis yields an act ivation energy for surface area reduction in sintering ZnO which compa res well with values reported in the literature.