Synthesis and electromagnetic characteristics of ZnO micro-crystal with varying morphology

Abstract

ZnO micro-crystals are prepared by hydrothermal reaction using PEG-20000/cyclohexane as additive, and Zn(OH)₄^2- and Zn(NH₃)₄²⁺ as precursors. Characterizations of the ZnO samples are conducted with X-ray diffraction (XRD), scanning electron microscopy (SEM) and selected area electron diffraction (SAED). The results show that the synthesized crystals belong to hexagonal crystalline system with typical morphology of ZnO aggregates composed of nano rod-like monocrystals which grew into various morphologies such as robust, tapered and clustered under different reaction conditions. The aggregates could be assembled with a controllable size of 2~4 μm. In the aid of PEG-20000, the specific face of crystal formed nucleus preferentially and then grew directionally. In addition, the tests of the microwave electromagnetic performance show a significant effect of the crystal morphology on the dielectric loss of ZnO. With the higher polar growing ability, the faster velocity, the shorter growing period and the more lattice defects, the polarization would become more intense to cause more dielectric loss of ZnO consequently.