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The internal luminescence quantum efficiency and color properties of AVO3 (A: Li, Na, K, Rb, and Cs), M2V2O7 (M: Mg, Ca, Sr, Ba, and Zn), and M3V2O8 (M: Mg, Ca, Sr, Ba, and Zn) have been investigated. These vanadate phosphors exhibited broadband emission from 400 nm to over 800 nm due to the one-electron charge transfer transition in the VO4 tetrahedra, and the color of the luminescent materials ranged from green to yellow-orange via white, corresponding to 0.277 < x < 0.494 and 0.389 < y < 0.488 on the CIE chromaticity diagram. We found that the luminescence quantum efficiency of the vanadate phosphors with VO4 tetrahedra was strongly enhanced by the strong interaction between V ions and the weak interaction between V and A(M) ions in the crystal structures. We hypothesize that the long exciton diffusion lifetime induced by these structural features enhanced luminescence, leading to high quantum efficiency.

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Combining infrared reflectivity, transport, susceptibility and several diffraction techniques, we find compelling evidence that CaCrO3 is a rare case of a metallic and antiferromagnetic transitionmetal oxide with a three-dimensional electronic structure. LSDA calculations correctly describe the metallic behavior as well as the anisotropic magnetic ordering pattern of C type: The high Cr valence state induces via sizeable pd hybridization remarkably strong next-nearest neighbor interactions stabilizing this ordering. The subtle balance of magnetic interactions gives rise to magneto-elastic coupling, explaining pronounced structural anomalies observed at the magnetic ordering transition.Strongly correlated electron systems including the wide class of transition-metal oxides exhibit a quite general relation between magnetic order and electrical conductivity [1]: ferromagnetism typically coexists with metallic conductivity, whereas insulators usually exhibit antiferromagnetism. It is always a challenge to understand exceptions from this rule. The rare observations of ferromagnetism in insulating transition-metal oxides most often are due to a particular type of orbital ordering [2]. The few examples of antiferromagnetic (AFM) metals, e.g., (La/Sr) 3 Mn 2 O 7 [3] or Ca 3 Ru 2 O 7 [4], are characterized by reduced electronic and structural dimensionality, and the antiferromagnetic order corresponds to a stacking of ferromagnetic (FM) layers. Here we report the discovery of a three-dimensional transition-metal oxide with metallic conductivity, antiferromagnetic exchange interactions, and C-type antiferromagnetic order: the perovskite CaCrO 3 .Perovskites containing Cr 4+ (CaCrO 3 , SrCrO 3 , and PbCrO 3 ) were already studied previously [5,6,7,8,9,10], but neither the details of the crystal structure nor the nature of the magnetic ordering are known. Only very recently evidence for C-type AFM order was reported in multi-phase samples of SrCrO 3 [10]. Regarding the conductivity, the existing data are controversial. In Refs. [7,9] CaCrO 3 was claimed to be metallic, but more recently insulating behavior has been reported [5]. A similar controversy persists also for SrCrO 3 , which should definitely be more metallic than CaCrO 3 due to the less distorted crystal structure, but metallic behavior was observed in Ref.[5] only under pressure. These controversies most likely are connected with the difficulty to prepare high-quality stoichiometric materials and with the lack of large single crystals.CaCrO 3 exhibits an orthorhombic GdFeO 3 -type perovskite structure and early magnetization measurements indicate a magnetic transition at 90 K [8], which is confirmed in our samples. Two electrons occupy the Cr 3d shell (S=1), rendering the material electronically similar to insulating RVO 3 [11] (also 3d 2 ) and to metallic (Ca/Sr)RuO 3 (4d 2 ) [12]. CaCrO 3 shows an unusually high transition-metal valence, Cr 4+ , which may lead to a small or even negative charge-transfer gap [13,14], i.e., holes in the O band. In CrO 2 with ruti...

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White-light-emitting materials have attracted considerable attention because of their applications, such as large-surface emitting devices. Inorganic phosphor films are expected to be applied to these devices because of good chemical stability; however, a substantial reduction of fabrication temperature is required for future industrial uses such as lighting materials fabricated onto flexible organic substrates. Here we show the optical properties of white-light-emitting metavanadate phosphors, AVO3 (A: K, Rb and Cs), and we report a new direct fabrication process for RbVO3 films onto flexible polyethylene terephthalate (PET) substrates by means of a vacuum ultraviolet irradiation using an excimer lamp. In addition, the (Ca,Sr,Pr)TiO3/a-Al2O3/RbVO3/PET heterostructure prepared by an excimer-laser-assisted metal-organic deposition process has demonstrated the possibility of colour modification for RbVO3 films on PET. Our findings suggest new possibilities for further development of large-surface emitting lighting devices.