Microwave Processing Laboratory - Other 95-2

Characterization of Microwave Processed ZnO

L. P. Martin,^* D. Dadon,^ D. Gershon,^* B. Levush,^* Y. Carmel,^* and M. Rosen^*
^Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, MD
^N.R.C.N., P.O. Box 9001, Beer Sheva, Israel
^Laboratory for Plasma Research, University of Maryland, College Park, Maryland

Ceramic Transactions 59, 399-407 (1995)

ABSTRACT. ZnO samples were prepared by microwave and conventional sintering processes using identical time-temperature profiles. Comparison of post-sintering ultrasonic properties as a function of residual porosity over the range of 0-35% indicated no difference in the velocity-porosity relations for the samples prepared by the two techniques. An empirical model was fit to the ultrasonic velocity and elastic moduli data. The real and imaginary parts of the permittivity of the samples processed by the two techniques possessed similar frequency dependence. In both cases there was an increase in the measured permittivity values with decreasing porosity; however, the microwave sintered samples had considerably higher values. The crystallographic features and the morphology of the samples were inferred from XRD and SEM examination, respectively. It was observed that there was significantly more densification at 850^oC for microwave sintering than for conventional sintering.