High pressure phase transition of ZnO/SiO2 core/shell nanospheres

Abstract

The structural phase transition of ZnO/SiO2 core/shell nanospheres was studied under high pressure using synchrotron X-ray diffraction. The results indicated that the wurtzite structure of the ZnO core is stable up to 11.5 GPa, and then transforms into rocksalt phase. The onset transition pressure is higher than those of the bulk and nano ZnO. It is worth noting that the phase transition from wurtzite to rocksalt is irreversible, which is obviously different from the uncapped bulk and nano ZnO. The pure rocksalt structure ZnO was first obtained at ambient conditions without catalyst or high temperature treatment. We suggested that the SiO2 shells play important roles in the phase transition of inner ZnO cores. The effects of the SiO2 shells on the phase transition of ZnO cores were discussed.