Papers by Author: Xi Yao

Abstract: The dielectric response of [110]-oriented 0.68PMN-0.32PT single crystal under dc electric field has been investigated. The characteristics of phase transition under temperature and dc electric field are provided. When electric field is above 2.3kV/cm, abnormal phase transition is induced by temperature and electric field, which corresponds to the phase transition from rhombohedral to orthorhombic ferroelectric phase. With increasing dc electric field, the stable temperature region of orthorhombic phase is expanded. The electric field-temperature (E-T) phase diagram of [110]-oriented 0.68PMN-0.32PT single crystals is presented. The polarization rotation in [110]-oriented single crystal is discussed.

Abstract: Four kinds of barium-ferrite-containing microcrystalline glass ceramics, such as BaFe12O19/SiO2, BaFe12O19/SiO2-B2O3, BaFe12O19/SiO2-B2O3-K2O and BaFe12O19/SiO2-Al2O3-K2O were prepared by citrate sol-gel process, in which inceptive formation temperatures varied from 850°C to 1100°C. The complex dielectric constant and complex permeability of those glass ceramics were measured at 0.1-5.0GHz, and the frequency dependence of complex dielectric constant and permeability was studied. The microcrystalline glass ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM).

Abstract: Semiconductor ZnSe nanocrystals (NCs)-doped SiO2 glasses (designated as ZnSe/SiO2 nanocomposites) were prepared successfully by using sol-gel method and in-situ growth technique. The nanocomposite was characterized by X-ray diffraction (XRD) patterns, UV-Vis absorption spectra and X-ray Photoelectron Spectroscopy (XPS). The XRD results show that ZnSe NCs is zinc blende structure and the mean size is smaller than 5nm in diameter. UV-Vis absorption spectra reveals that the size of the NCs is influenced by synthesis conditions such as doping concentration and thermal treatment, and XPS together with XRD can prove that silica matrix plays an important role in enhancing the NCs’ stability.