Qiang Dong

Structural consideration on the emission properties of Eu{sup 2+}-doped Li{sub 2}BaMgP{sub 2}O{sub 8} and Na{sub 2}BaMgP{sub 2}O{sub 8} orthophosphates

Li{sub 2}BaMgP{sub 2}O{sub 8} and Na{sub 2}BaMgP{sub 2}O{sub 8} were synthesized by a standard solid state reaction. Structural analyses have revealed that Li{sub 2}BaMgP{sub 2}O{sub 8} is a member of the olgite family, as is the case with Na{sub 2}BaMgP{sub 2}O{sub 8}. The layer-framework build up by corner-sharing MgO{sub 6} octahedra and PO{sub 4} tetrahedra twists around C{sub 3} axes to match the size of B-site cation (Li{sup +} or Na{sup +}). This twisting affects the coordination number for the B-site cation and unit cell size. Eu-doped Li{sub 2}BaMgP{sub 2}O{sub 8} and Na{sub 2}BaMgP{sub 2}O{sub 8} exhibited intense violet-blue emission under ultraviolet excitation. They were characterized by two emission centers; Eu{sup 2+} ions replacing A-site cations (Ba{sup 2+}) and B-site cations (Li{sup +} or Na{sup +}). The B-site Eu{sup 2+} emission was very sensitive to the twisting behavior caused by original B-site cation. - Graphical abstract: Emission properties of Eu{sup 2+}-doped M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} (M{sup I}: Li, Na) are discussed from the viewpoint of the host crystal structure solved by X-ray powder diffraction technique and Raman spectroscopy. Highlights: Black-Right-Pointing-Pointer Olgite-type Li{sub 2}BaMgP{sub 2}O{sub 8} has been prepared by a solid state reaction. Black-Right-Pointing-Pointer Crystal structure of M{sup I}{submorexa0» 2}BaMgP{sub 2}O{sub 8} changes, depending on M{sup I} ion size. Black-Right-Pointing-Pointer Eu{sup 2+}-doped M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} exhibits violet-blue emission under ultraviolet irradiation. Black-Right-Pointing-Pointer Emission from M{sup I}{sub 2}BaMgP{sub 2}O{sub 8} is characterized by two Eu{sup 2+} emission centers. Black-Right-Pointing-Pointer One emission component of the two is sensitive to the structural change induced by M{sup I}.«xa0less

Preparation and crystal structure of a new bismuth vanadate, Bi{sub 3.33}(VO{sub 4}){sub 2}O{sub 2}

Abstract Single crystals of a new bismuth vanadate, Bi3.33(VO4)2O2 was prepared by hydrothermal reaction using a hydrated sodium bismuthate, NaBiO3·nH2O as one of the starting compounds. The crystal structure was determined by using single crystal X-ray diffraction data. This compound crystallizes in the triclinic space group P 1 ¯ (#2) with axa0=xa07.114(1), bxa0=xa07.844(2), cxa0=xa09.372(2)xa0A, αxa0=xa0106.090(7), βxa0=xa094.468(7) and γxa0=xa0112.506(8)°, Zxa0=xa02 and the final R factors are R1xa0=xa00.052 and wR2xa0=xa00.14 for 2085 unique reflections. The crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO4 tetrahedra, and one of four bismuth atoms is statistically distributed in the splitting sites with the distance of 0.83xa0A. This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation and its activity was less than that of monoclinic BiVO4.