Two polymorphs of K 3 YSi 2 O 7 , crystallizing in the space groups P6 3 /mmc (1) and P6 3 /mcm (2) can be synthesized by high temperature flux crystal growth. The flux growth conditions can be fine-tuned to yield a phase pure sample of polymorph (2), however, not of polymorph (1), which always co-crystallizes with polymorph (2). Polymorph (2) was found to exhibit intrinsic bluish-white light emission. Further studies determined that doping europium and dysprosium onto the yttrium site of this polymorph could readily tune the luminescence, with the purest white light emission found for the K 3 YSi 2 O 7 : 10% Dy, 0.1% Eu composition (K 3 Y 0.899 Dy 0.1 Eu 0.001 Si 2 O 7 ) (2-Dy,Eu).

Single crystals of KBaMnO 4 and KBaAsO 4 were grown using the hydroflux method and characterized by single crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Pnma with a = 7.7795(4) Å, b = 5.8263(3) Å, and c = 10.2851(5) Å for the manganate and a = 7.7773(10) Å, b = 5.8891(8) Å, and c = 10.3104(13) Å for the arsenate. The materials exhibit a threedimensional crystal structure consisting of isolated MnO 4 3or AsO 4 3tetrahedra, with the charge balance maintained by K + and Ba 2+. Each tetrahedron is surrounded by six K + and five Ba 2+ , and shares its corner/edge with KO 10 polyhedra and corner/edge/face with BaO 9 polyhedra, respectively. The crystal growth, crystal structure and magnetic properties are discussed.

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Crystals of the first sodalite-type zeolite containing an all-iron framework, a ferrolite, Ba (Fe O )Na (OH) ⋅x H O, were synthesized using the hydroflux method in nearly quantitative yield. Ba (Fe O )Na (OH) ⋅x H O crystallizes in the cubic space group Pm3‾m with a=10.0476(1) Å. Slightly distorted FeO tetrahedra are linked to form Fe O and Fe O rings, which in turn yield channels and internal cavities that are characteristic of the sodalite structure. Barium, sodium, and hydroxide ions and water molecules are found in the channels and provide charge balance. Magnetic measurements indicate that the ferrolite exhibits magnetic order up to at least 700 K, with the field-cooled and zero-field-cooled curves diverging. Analysis of the Fe Mössbauer spectra revealed two spectral components that have equal spectral areas, indicating the presence of two subsets of iron centers in the structure. Dehydrated versions of the ferrolite were also prepared by heating the sample.

Single crystals of the new compound KBaAsO4 are prepared from a mixture of As2O3, Ba(NO3)2, KOH, and H2O (autoclave, 230 °C, 24 h) and single crystals of KBaMnO4 are obtained from a mixture of Ba(OH)2, KMnO4, KOH, NaOH, and H2O (autoclave, 230 °C, 12 h).