Cubic and hexagonal sodium yttrium fluoride were successfully synthesized from yttrium nitrate, sodium fluoride and polyethanediol in propanetriol solvent under a facile hydrothermal route. By regulating the molar ratio of yttrium and fluoride, hydrothermal temperature and reaction time, the phase and shape of sodium yttrium fluoride were commendably controlled. The as-prepared products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive X-ray spectrum （EDS） techniques. It was revealed that the hollow-structured Na（Y1.5Na0.5）F6 nanotubes self-assembled and arrayed orientedly to be bamboo raft-shaped. The formation of hexagonal Na（Y1.5Na0.5）F6 nanotube arrays was attributed to solid-liquid-solid process and Oswald ripening. This study provided a simple method to prepare hexagonal bamboo raft-shaped Na（Y1.5Na0.5）F6 on a large scale, which broadened their practical applications.
Tetragonal structural(t-NdVO4)nanorod-arrays were fabricated by simple one-pot hydrothermal method.The phase,morphology and microstructure of NdVO4 were characterized by X-ray diffractometer,scanning electron microscope(SEM),transmission electron microscope(TEM),dispersive X-ray spectrometer(EDS)and selected area electron diffraction(SAED)techniques.t-NdVO4 nanorods are single-crystalline with a length of 100 nm and a diameter of 25 nm,which grow orientally along the direction of(112)crystalline plane and self-assemble to form nanorod-arrays.The results show that Eu^3+-doping interrupts the formation of NdVO4 nanorod-arrays,and then leads to the red-shift of the strongest luminescence emission of Nd3+transition from 4D3/2 state to 4I11/2 and decreases its intensity of the fluorescence emission at 400 nm sharply.The research results have some reference values to optimize the photoluminescence performance of rare earth vanadates.
Li TIANShan-min CHENQiang LIUJie-ling WURui-ni ZHAOShan LILi-juan CHEN
Monodisperse sodium yttrium fluoride com sticks with hexagonal nanostructure were successfully prepared by a facile and repeatable precipitation transformation method. The phase and morphology of the products were characterized with X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The growth mechanism was studied, indicating that the initial generated Y（OH）3 gradually translated into YF3 and then transformed into com stick-like H-NaYF4 nanoparticles owing to the crucial role of fluorine ions in the solution. The up-conversion （UC） luminescence properties of H-NaYF4：20%Yb3＋,2%Er3＋ nanocrystals were discussed. The intensive green emission in the range of 510-570 nm was attributed to the （2Hll/2, 4S3/2）----4It5/2 transition and the weaker red emission between 640 and 680 nm was originating from the 4F9/2----4115/2 transition.
