The new lanthanum vanadium oxyselenides LaVSeO, LaVSeO, LaVSeO, LaVSeO, and LaVSeO were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined using single-crystal and powder X-ray diffraction experiments. LaVSeO and LaVSeO adopt known structure types, whereas LaVSeO, LaVSeO, and LaVSeO crystallize in hitherto unknown structure types. The main building blocks of these compounds are chains of edge-sharing VSe, VSeO, and/or VSeO octahedra, linked together by edge-sharing OLa and/or OLaV tetrahedra forming fluorite-like ribbons. LaVSeO, LaVSeO, and LaVSeO contain only V(iii) ions, whereby LaVSeO and LaVSeO contain mixtures of either V(iii)/V(iv) or V(iii)/V(v) cations. Magnetic measurements indicate Curie-Weiss paramagnetism and magnetic ordering of the vanadium moments at low temperatures. More precisely, we observe antiferromagnetism for LaVSeO, metamagnetism for LaVSeO, ferromagnetism for LaVSeO and a complex magnetic structure for LaVSeO.
The oxonitridosilicates RE 6-x Ca 1.5x Si 11 N 20 O (RE = Yb, Lu; x ≈ 2.2) were synthesized starting from REF 3 , CaH 2 , and "Si(NH) 2 " in a radiofrequency furnace at 1600 or 1400°C, respectively. The crystal structure was solved and refined from singlecrystal X-ray diffraction data of dark red Yb 6-x Ca 1.5x Si 11 N 20 O crystals in the trigonal space group P31c (no. 159) with a = 9.8281(10), c = 10.5968(13) Å and Z = 2. The structure represents a filled variant of the Er 6 Si 11 N 20 O structure type, in which the charge difference caused by substitution of trivalent Yb 3+ with bivalent Ca 2+ is balanced by occupation of an additional [a]
The oxonitridosilicate La 7 Sr[Si 10 N 19 O 3 ] : Eu 2 + and its substitutional variants RE 8-x AE x [Si 10 N 20-x O 2 + x ] : Eu 2 + with RE = La, Ce; AE = Ca, Sr, Ba and 0 � x � 2 were synthesized starting from REN, SrN/Ca 3 N 2 /Ba 2 N, SiO 2 , amorphous Si 3 N 4 and Eu 2 O 3 as doping agent at 1600 °C in a radiofrequency furnace. The crystal structure of La 7 Sr[Si 10 N 19 O 3 ] was solved and refined based on single-crystal X-ray diffraction data. La 7 Sr[Si 10 N 19 O 3 ] crystallizes in the orthorhombic space group Pmn2 1 (no. 31). The crystal structures of the isotypic compounds RE 8-x AE x -[Si 10 N 20-x O 2 + x ] were confirmed by Rietveld refinements based on powder X-ray diffraction data using the single-crystal data of La 7 Sr[Si 10 N 19 O 3 ] as starting point. Crystal structure elucidation reveals a 3D network of vertex sharing SiN 4 and SiN 2 (N 1/2x/4 O 1/2 + x/4 ) 2 (0 � x � 2) tetrahedra. When excited with UV to blue light, La 7 Sr[Si 10 N 19 O 3 ] : Eu 2 + shows amber luminescence with λ em = 612 nm and fwhm = 84 nm/2194 cm À 1 , which makes it interesting for application in amber phosphorconverted light emitting diodes.
The nitridosilicate CaLu[Si 4 N 7-2x C x O x ] (x � 0.3) was synthesized by carbothermal reduction and nitridation starting from CaH 2 , Lu 2 O 3 , graphite and amorphous Si 3 N 4 at 1550 °C in a radiofrequency furnace. CaLu[Si 4 N 7-2x C x O x ] (x � 0.3) crystallizes isotypically to many previously known M II M III Si 4 N 7 compounds in the space group P6 3 mc, as was confirmed by Rietveld refinement based on powder X-ray diffraction data. Incorporation of carbon into the crystal structure as a result of the carbothermal synthesis route was confirmed by 13 C and 29 Si MAS NMR spectroscopy. For the first time in the M II M III Si 4 N 7 compound class, complementary EDX measurements suggest that simultaneous incorporation of oxygen compensates for the negative charge excess induced by carbon, resulting in an adjusted sum formula, CaLu[Si 43) shows an emission maximum in the blue spectral region (λ em = 484 nm; fwhm = 4531 cm À 1 ) upon doping with Ce 3 + , whereas Eu 2 + -doped CaLu[Si 4 N 7-2x C x O x ] (x � 0.3) exhibits a yellow-green emission (λ em = 546 nm; fwhm = 3999 cm À 1 ).
Single-crystalline domains in intergrown microcrystalline material of the new compounds Ba 22.5 + x La 55 À x -[Si 129 N 240 À x O x ]O 3 :Ce 3 + and Ba 25.5 + x La 77 À x [Si 170 N 312 À x O 9 + x ]O 4 :Ce 3 + were identified by transmission electron microscopy (TEM). Precise diffraction data from these domains were collected with microfocused synchrotron radiation so that crystal structure elucidation of the complex disordered networks became possible. They are composed of two different interconnected slabs of which one is similar in both compounds, which explains their notorious intergrowth. The distribution of Ba and La is indicated by the analysis of bondvalence sums and by comparison with isostructural Sr 28.5 +x La 75 À x [Si 170 N 312 À x O 9 + x ]O 4 . Ce 3 + doping leads to yellow luminescence. This is a showcase that highlights the discovery and accurate characterization of new compounds relevant for luminescence applications from heterogeneous microcrystalline samples by exploiting the capability of the combination of TEM and diffraction using the latest focusing techniques for synchrotron radiation.
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