The cis-[WO2F4]2- anion is inherently acentric and contains polarizable WO bonds, making it a good candidate for second-harmonic generation (SHG). However, the orientational disorder commonly found in crystal structures containing [WO2F4]2- must be understood as a first step toward engineering a polar SHG material with this anion. The strategy of crystallizing the [WO2F4]2- anion with two different cations, which was successful in ordering the related [NbOF5]2- and cis-[MoO2F4]2- anions, is able to order one of the two WO bonds. Close inspection of bond lengths and anisotropic thermal ellipsoids in disordered [WO2F4]2- compounds gives insight into disorder mechanisms and suggests strategies for eliminating orientational disorder. Crystal data:  for [pyH]2[Cu(py)4(WO2F4)2], tetragonal, space group I4122 (No. 98), with a = 11.339(2) Å, c = 30.489(6) Å, and Z = 4; for Cu(pyz)2WO2F4·(pyz)(H2O) polymorph I, tetragonal, space group I4/mcm (No. 140), with a = 9.745(1) Å, c = 16.565(3) Å, and Z = 4; for Cu(pyz)2WO2F4·(pyz)(H2O) polymorph II, tetragonal, space group P4/mmm (No. 123), with a = 6.886(3) Å, c = 8.300(2) Å, and Z = 1.

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structure structure (solids and liquids) D 2000 -009The Polar [WO 2 F 4 ] 2− Anion in the Solid State.-The crystal structures of the compounds (IV) and (V) are solved by single-crystal X-ray analysis. Compound (IV) crystallizes in the tetragonal space group I4 1 22 with Z = 4. Its structure is built from [Cu(py) 4 (WO 2 F 4 ) 2 ] 2− anions hydrogen bonded to pyridinium (pyH + ) cations. Compound (V) is obtained in two polymorphic forms in an overall yield of 60%. Polymorph A crystallizes in the tetragonal space group I4/mcm with Z = 4, whereas polymorph B crystallizes in the tetragonal space group P4/mmm with Z = 1. The copper cations in (V) are bridged by four pyrazine ligands to form [Cu(pyz) 4/2 ] 2n+ n infinite square nets in the (001) plane. The axial copper positions are coordinated by [WO 2 F 4 ] 2− anions, which link the infinite nets together in the c direction. The resulting three-dimensional structure contains channels which are filled with H 2 O and pyrazine solvent molecules. The [WO 2 F 4 ] 2− anion has cis-configuration in all complexes. -(HEIER, KEVIN R.; NORQUIST, ALEXANDER J.; HALASYAMANI, P. SHIV; DUARTE, ANGEL; STERN, CHARLOTTE L.; POEPPELMEIER, KENNETH R.; Inorg. Chem. 38 (1999) 4, 762-767; Dep.

A comparative study of the structural, microstructural and magnetic properties of CrO 2 thin films grown onto (110) and (100) TiO 2 rutile single crystal substrates by chemical vapor deposition (CVD), using CrO 3 as chromium precursor and either oxygen or argon as carrier gas is presented. Our results show that growth under argon carrier gas leads to high quality CrO 2 epilayers with structural and magnetic properties similar to those obtained using the more standard oxygen carrier gas. Furthermore, we interpret the larger magnetic coercivity observed for the (110) oriented films in terms of their microstructure, in particular of the highest strain and edge roughness of the building structures of the CrO 2 epilayers, which are settled by the substrate crystallographic orientation. * [19][20][21][22]. But the studies on chromium dioxide have not been limited to fundamental or applied science. Indeed, CrO 2 has been used in industry covering a wide range of applications e.g. audio, video, instrumentation and computer technology due to its exceptional properties as a magnetic storage material [13].Although some attempts have been pursued to grow thin films of the single CrO 2 compound by physical vapor deposition methods [23][24][25], only chemical vapor deposition (CVD) has shown to lead to high quality CrO 2 layers [26][27][28][29][30]. CrO 2 epitaxial layers are currently grown on TiO 2 rutile phase and sapphire substrates by CVD using CrO 3 as the chromium precursor, which is carried out into the reaction zone by an oxygen flux. While chromium precursors other than CrO 3 , e.g. Cr 8 O 21 [31] and CrO 2 Cl 2 [8,10], have also been used in the CVD of CrO 2 yielding films with similar properties, the use of an oxygen flux has been pointed out as critical for the overall CrO 2 synthesis process. To our knowledge, only the work of Ivanov et al. [31] briefly refers that the use of argon as carrier gas makes the process very inefficient and leads to films with poorer crystallinity.Currently, the demand for fast and cost-efficient fabrication processes of high-quality materials and devices is on the agenda. Hence, an in-depth study of the feasibility of growing high quality epitaxial films of CrO 2 using argon as carrier gas becomes crucial, especially because of the well-known price difference between the two gases, with cost advantage to Page 3 of 27 argon. Besides, argon is a more user-friendly gas. Therefore, the fact that the use of argon could eventually limit the CrO 2 synthesis reaction may be seen as a drawback to the envisaged scaling-up of the CrO 2 CVD process at an industrial level.This work reports on the synthesis and properties of CrO 2 thin films grown onto single crystal TiO 2 rutile substrates by CVD, using CrO 3 as chromium precursor and either oxygen or argon as carrier gas. A comparative study of the structural, microstructural and magnetic properties of the different films are presented. Experimental detailsThe CrO 2 films were prepared in a tubular single-zone CVD furnace with independent control...

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