Direct preparation of K0.5Na0.5NbO3 powders

K_0.5Na_0.5NbO₃ powders have been directly synthesized by an alternative solid–state method. Stoichimometric mixture of ammonium niobium oxalate and C₄H₄O₆KNa·4H₂O were calcined in temperature range from 500 to 800 °C for 3 h. The precursor and calcination products were characterized with respect to stoichiometry, purity, crystalline structure, particle size and powder morphology using X–ray diffraction (XRD), X‐ray fluorescence (XRF) spectrometer, scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectra, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and UV–Vis diffuse reflectance (UV–Vis) spectroscopy. XRD and XRF results reveal that stoichiometric K_0.5Na_0.5NbO₃ powders could be synthesized by the method. The particle size is about 68 nm for the precursor calcined at 500 °C according to XRD data, which is in good agreement with SEM data. The average band gap energy is estimated to be 3.18 eV by UV–vis diffuse reflectance spectra. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reaction of dichloromaleic anhydride with 1,8-diaminonaphthalene: Synthesis and X-ray diffraction structure of 8,9-dichloropyrrolo[1,2-a]perimidin-10-one

The reaction of dichloromaleic anhydride with 1,8-diaminonaphthalene in refluxing toluene or 1,2-dichloroethane produces the new heterocyclic compound 8,9-dichloropyrrolo[1,2-a]perimidin-10-one in low yields. 8,9-Dichloropyrrolo[1,2-a]perimidin-10-one has been isolated by column chromatography and characterized in solution by IR, ¹H NMR, and UV/vis spectroscopies. The solid-state structure was unequivocally established by single-crystal X-ray diffraction analysis. 8,9-Dichloropyrrolo[1,2-a]perimidin-10-one crystallizes in the monoclinic space group P2 ₁/c, a = 7.475(1)Å, b = 10.650(2)Å, c = 14.468(2)Å, = 94.478(2)°, V = 1148.3(3) ų, Z = 4, and d _calc = 1.672 Mg/m³; R = 0.0289, R _w = 0.0762 for 1644 reflections with I > 2(I). The nature of the HOMO and LUMO in 8,9-dichloropyrrolo[1,2-a]perimidin-10-one has been determined by extended Hückel molecular orbital calculations, and these data are discussed relative to the cyclic voltammetric data obtained at a platinum electrode.     

微波法制备CaMoO4:Tb3+,Eu3+白色荧光粉及其发光性能研究

通过微波法制备了CaMoO4:Tb3+,Eu3+白色荧光粉.采用X射线粉末衍射仪、扫描电子显微镜和荧光光谱仪对样品材料的结构、形貌和发光性能进行了表征.分别讨论了在不同助剂、不同反应浓度、不同反应温度及稀土离子Eu3+和Tb3+共掺比例变化对荧光粉的发光性能的影响.结果表明:不加活性剂所得CaMoO4:Tb3+,Eu3+样品在反应浓度为0.06 mol/L、反应温度为120℃时发光性能最好;通过调节CaMoO4:Tb3+,Eu3+荧光粉中稀土离子Eu3+和Tb3+共掺比例荧光粉的发光颜色可以很容易地从冷白光变为暖白光.