The powder crystals of RMnO 3 (R=Er, Tm) with hexagonal and orthorhombic structures were prepared under hydrothermal conditions. The different structural phases of the title compounds were controllably formed from different kinds of precursors at different reaction temperatures. All of the samples were characterized by powder X-ray diffraction, scanning electron microscopy, inductively coupled plasma analysis, and variable temperature magnetic susceptibility. Their structures were refined by Rietveld method from powder X-ray diffraction data. The measurement of magnetic behavior shows antiferromagnetic orderings at Neel temperatures around 80 and 40 K for the hexagonal and orthorhombic phases, respectively.
A series of double perovskites RSrMnFeO_6(R=La,Pr,Nd,Sm) was synthesized under mild hydrothermal conditions.Crystal growths of the samples were sensitive to alkalinity,temperature,filling fraction,and composition of initial reaction mixture.The desired series of compounds belongs to the class of AA'BB'O_6 perovskites with a random distribution of Mn and Fe atoms over the B-cation sub-lattice.Their structures show the distorted orthorhombic symmetry with space group Pnma.The shapes and sizes of the crystals were analyzed on a Rigaku JSM-6700F by scanning electron microscopy.Analysis done by XPS,Mssbauer spectroscopy and iodometric titration reveals that Mn and Fe ions have +4 and +3 oxidation states,respectively.
ZHANG Gang-hua YUAN Hong-ming CHEN Yan LI Wei-juan YANG Mei-qi FENG Shou-hua
Hausmannite Mn3O4 nanoparticles were successfully prepared via a facile one-step solvothermal route with Mn(CH3COO)2·4H2O as manganese source in the mixed solvent of acetone and water.Powder X-ray diffraction(XRD),Fourier transform infrared(FTIR) spectrometry and transmission electron microscopy(TEM) were used to characterize Mn3O4 nanoparticles.It was found that the particle size could be tailored by varying the synthesis temperature.On the whole,the particle size becomes larger with the rising of solvothermal reaction temperature.But there is no linear relation between them.According to the different temperatures(60―140 °C),the average particle size is from about 9 nm to 15 nm.Magnetic properties of Mn3O4 samples prepared at 60,100 and 140 °C were studied via a superconducting quantum interference device(SQUID),respectively.
ZnO particles were prepared by Au-catalyzed vapor phase transport method on silicon substrate. Scanning electron microscopy(SEM) images show many ZnO particles were formed on the sample surface. They grew up layer by layer along the c-axis, which was confirmed by the results of X-ray diffraction(XRD). The morphology of ZnO particles is close to hemisphere and its formation process could be seen from the SEM image. The room temperature photoluminescence(PL) measurement revealed a narrow UV emission peak at 3.27 eV and a broad green emission peak at 2.45 eV, which was caused by the near-band-edge and deep-level emissions.
HU Shi-qi HUANG Ke-ke HOU Chang-min YUAN Hong-ming HU Bin FENG Shou-hua
