Analysis of ultrasonic velocity measurements on sintering zinc oxide

Abstract

Abstract A technique is presented for accurate measurement of the longitudinal wave velocity up to 1050 °C in sintering powder compacts. The technique uses laser generation and contact detection of the ultrasonic signal. Representative results are presented for heating cycles performed upon sintering ZnO powder compacts, and upon a pre-sintered dense ZnO sample. The data demonstrate the capability for performing in-situ longitudinal wave velocity measurements at high temperatures, and in attenuative materials such as sintering ceramic powder compacts. In addition, the data demonstrate the sensitivity of ultrasonic velocity measurements to changes within the sintering compact which are not detectable by dimension measurement alone. A novel application of ultrasonic velocity measurements performed in-situ on sintering ZnO is presented. This application is based upon interpretation of longitudinal wave velocity measurements in the context of existing models treating surface area reduction during sintering. A previously observed correlation between the longitudinal wave ultrasonic velocity and the specific surface area facilitates this interpretation. The analysis yields an activation energy for surface area reduction in sintering ZnO which compares well with values reported in the literature.