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Single crystals of new oxyborates, Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}, were prepared at 1370 deg. C in air using B{sub 2}O{sub 3} as a flux. They were colorless and transparent with block shapes. X-ray diffraction analysis of the single crystals revealed Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3} to be isostructural. The X-ray diffraction reflections were indexed to the orthorhombic Pnma (No. 62) system with a=9.3682(3) A, b=9.4344(2) A, c=9.3379(3) A and Z=4 for Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and a=9.3702(3) A, b=9.4415(3) A, c=9.3301(2) A and Z=4 for Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}. The crystal structures of Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3} are novel warwickite-type superstructures having ordered arrangements of Mg and Nb/Ta atoms. Polycrystals of Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} prepared by solid state reaction at 1200 deg. C in air showed broad blue-to-green emission with a peak wavelength of 470 nm under 270 nm ultraviolet excitation at room temperature. - Graphical abstract: Single crystals of new oxyborates, Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}, were synthesized by a self flux method. They crystallize in novel warwickite-type superstructuresmore » having ordered arrangements of Mg and Nb/Ta atoms. Highlights: > Single crystals of two new oxyborates, Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} and Mg{sub 5}TaO{sub 3}(BO{sub 3}){sub 3}, were prepared using B{sub 2}O{sub 3} as a flux. > Both oxyborates crystallize in isotypic novel warwickite-type superstructures with seven-fold coordinated Nb/Ta atoms. > Polycrystalline sample of Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} was prepared by solid state reaction. > Polycrystalline Mg{sub 5}NbO{sub 3}(BO{sub 3}){sub 3} exhibits broad blue-to-green emission with a peak wavelength of 470 nm under 270-nm excitation.« less

Colorless and transparent single crystals of Ca3Sn2.2Ti0.8Al2O12, which emit blue–white light under ultraviolet light, were prepared by heating a mixture of oxides and calcium carbonate with a calcium and aluminum-rich composition at 1500 °C. Single crystal X-ray diffraction revealed that the crystal structure is the garnet-type with a cubic cell parameter (a=12.5309(3) A) and the space group, Ia 3¯d (R1=0.0277, wR2=0.0663, and S=1.367 for all data). The structural formula is presented as Ca3[Sn0.96Ti0.04]octa[Al0.67Ti0.24Sn0.09]tetraO12. Polycrystalline solid solutions of Ca3Sn3−xTixAl2O12 were prepared by solid state reaction in air at 1370 °C with nominal titanium contents from x=0.6 to 1.4. The refined unit cell parameter decreased with increasing x. A broad blue–white emission with a peak wavelength of 465 nm was observed for the solid solutions at room temperature.

X-ray fluorescence analysis based on electron channeling effects in transmission electron microscopy (TEM) was performed on Ca 2 SnO 4 phosphor materials doped with Eu 3+ /Y 3+ at various concentrations, which showed red photoluminescence associated with the 5 D 0 – 7 F 2 electric dipole transition of Eu 3+ ions. The method provided direct information on which host element site dopant elements occupy, the results of which were compared with those of X-ray diffraction (XRD)–Rietveld analysis. The obtained results indicated that while it is not favorable for a part of Eu 3+ to occupy the smaller Sn 4+ site, this is still energetically better than creating Ca vacancies or any other of the possible charge balance mechanisms. The local lattice distortions associated with dopant impurities with different ionic radii were also examined by TEM–electron energy-loss spectroscopy (TEM–EELS). The change in PL intensity as a function of dopant concentration is discussed based on the experimental results, although the general concept of concentration quenching applies.

Single crystals of iron(II) pyroborate, Fe2B2O5, were prepared at 1000–1050 °C under an argon atmosphere. The crystals were transparent, yellowish in color and needle-like or columnar. The crystal structure of Fe2B2O5 was analyzed by single-crystal X-ray diffraction. Refined triclinic unit cell parameters were a=3.2388(2), b=6.1684(5), c=9.3866(8) A, α=104.613(3)°, β=90.799(2)° and γ=91.731(2)°. The final reliability factors of refinement were R1=0.020 and wR2=0.059 [I > 2σ(I)]. Transmittance over 50% in the visible light region from 500 to 750 nm was observed for a single crystal of Fe2B2O5 with a thickness of about 0.3 mm. The light absorption edge estimated from a diffuse reflectance spectrum was at around 350 nm (3.6 eV). Magnetic susceptibility was measured for single crystals at 4–300 K. Fe2B2O5 showed antiferromagnetic behavior below the Neel temperature, TN≈70 K, and the Weiss temperature was TW=36 K. The effective magnetic moment of Fe was 5.3μB.