摘要：A series of red emitting ZnTiO3 phosphors co-doped with Eu3+ and alkali metal ions（Li+, Na+ and K+...A series of red emitting ZnTiO3 phosphors co-doped with Eu3+ and alkali metal ions（Li+, Na+ and K+） was prepared by sol-gel method. The crystal structure of the phosphors was investigated by using X-ray diffraction（XRD） and transmission electron microscopy（TEM） after annealing at 700 ℃. The results show that the crystal structure belongs to the hexagonal phase of ZnTiO3 with space group R-3:R. The influence of site occupancy of different alkali metal ions on the emission of ZnTiO3:Eu3+ phosphors was investigated in detail. The emission intensity was significantly enhanced by introducing alkali metal ions. In contrast to Eu3+ singly doped ZnTiO3, the red emission intensities of ZnTiO3:Eu3+ with 4 mol% alkali metal ions（Li+, Na+, K+） were enhanced by about 2.1, 1.7 and 1.4 times, respectively. In addition, the Commission Internationale Ed I’eclairage（CIE） chromaticity coordinates of ZnTiO3:Eu3+, Li+（0.672, 0.328） are quite similar to the National Television Standard Committee（NTSC） standard values for the red（0.670, 0.380）.显示全部
摘要：Geometric and electronic structures of three polymorphs of BiPO4（m MBIP, n MBIP and HBIP） have be...Geometric and electronic structures of three polymorphs of BiPO4（m MBIP, n MBIP and HBIP） have been investigated by the first-principles calculations. The results show that PO4 tetrahedron in n MBIP is distorted most, and m MBIP possesses minimum effective mass of carriers in three polymorphs of BiPO4. Further, the leading role of inductive effect of dipole moment or effective mass of carries in the separation of electron-hole pairs is analyzed. Based on the fact that n MBIP has higher photocatalytic activity than m MBIP, it can be inferred that the inductive effect of dipole moment deriving from distorted PO4 tetrahedron is the dominant factor affecting the separation efficiency of carries. The calculated results represent that n MBIP has more appropriate redox potential and narrower band gap than others. These findings may provide meaningful guidance for further understanding on the relationship between unique crystal structure and photocatalytic activity of BiPO4.显示全部
