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null (Ed.)Two new alkali vanadate carbonates with divalent transition metals have been synthesized as large single crystals via a high-temperature (600 °C) hydrothermal technique. Compound I , Rb 2 Mn 3 (VO 4 ) 2 CO 3 , crystallizes in the trigonal crystal system in the space group P 3̄1 c , and compound II , K 2 Co 3 (VO 4 ) 2 CO 3 , crystallizes in the hexagonal space group P 6 3 / m . Both structures contain honeycomb layers and triangular lattices made from edge-sharing MO 6 octahedra and MO 5 trigonal bipyramids, respectively. The honeycomb and triangular layers are connected along the c -axis through tetrahedral [VO 4 ] groups. The MO 5 units are connected with each other by carbonate groups in the ab -plane by forming a triangular magnetic lattice. The difference in space groups between I and II was also investigated with Density Functional Theory (DFT) calculations. Single crystal magnetic characterization of I indicates three magnetic transitions at 77 K, 2.3 K, and 1.5 K. The corresponding magnetic structures for each magnetic transition of I were determined using single crystal neutron diffraction. At 77 K the compound orders in the MnO 6 -honeycomb layer in a Néel-type antiferromagnetic orientation while the MnO 5 triangular lattice ordered below 2.3 K in a colinear ‘up–up–down’ fashion, followed by a planar ‘Y’ type magnetic structure. K 2 Co 3 (VO 4 ) 2 CO 3 ( II ) exhibits a canted antiferromagnetic ordering below T N = 8 K. The Curie–Weiss fit (200–350 K) gives a Curie–Weiss temperature of −42 K suggesting a dominant antiferromagnetic coupling in the Co 2+ magnetic sublattices.more » « less
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Abstract Electrospray ionization (ESI) can produce a wide range of gas‐phase uranyl (UO22+) complexes for tandem mass spectrometry studies of intrinsic structure and reactivity. We describe here the formation and collision‐induced dissociation (CID) of [UO2(NO3)3]−and [UO2(NO3)2(O2)]−. Multiple‐stage CID experiments reveal that the complexes dissociate in reactions that involve elimination of O2, NO2, or NO3, and subsequent reactions of interesting uranyl‐oxo product ions with (neutral) H2O and/or O2were investigated. Density functional theory (DFT) calculations reproduce experimental results and show that dissociation of nitrate ligands, with ejection of neutral NO2, is favored for both [UO2(NO3)3]−and [UO2(NO3)2(O2)]−. DFT calculations also suggest that H2O adducts to products such as [UO2(O)(NO3)]−spontaneously rearrange to create dihydroxides and that addition of O2is favored over addition of H2O to formally U(V) species.
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This Review highlights basic and transition metal conducting and semiconducting oxides. We discuss their material and electronic properties with an emphasis on the crystal, electronic, and band structures. The goal of this Review is to present a current compilation of material properties and to summarize possible uses and advantages in device applications. We discuss Ga 2 O 3 , Al 2 O 3 , In 2 O 3 , SnO 2 , ZnO, CdO, NiO, CuO, and Sc 2 O 3 . We outline the crystal structure of the oxides, and we present lattice parameters of the stable phases and a discussion of the metastable polymorphs. We highlight electrical properties such as bandgap energy, carrier mobility, effective carrier masses, dielectric constants, and electrical breakdown field. Based on literature availability, we review the temperature dependence of properties such as bandgap energy and carrier mobility among the oxides. Infrared and Raman modes are presented and discussed for each oxide providing insight into the phonon properties. The phonon properties also provide an explanation as to why some of the oxide parameters experience limitations due to phonon scattering such as carrier mobility. Thermal properties of interest include the coefficient of thermal expansion, Debye temperature, thermal diffusivity, specific heat, and thermal conductivity. Anisotropy is evident in the non-cubic oxides, and its impact on bandgap energy, carrier mobility, thermal conductivity, coefficient of thermal expansion, phonon modes, and carrier effective mass is discussed. Alloys, such as AlGaO, InGaO, (Al x In y Ga 1− x− y ) 2 O 3 , ZnGa 2 O 4 , ITO, and ScGaO, were included where relevant as they have the potential to allow for the improvement and alteration of certain properties. This Review provides a fundamental material perspective on the application space of semiconducting oxide-based devices in a variety of electronic and optoelectronic applications.more » « less