Main Fields and Results of Research Activities

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  Results of fundamental and applied research

  
  

  1. The method of synthesis of rare-earth and alkaline-earth element cuprates by purpose-oriented doping of cationic sites in the perovskite structure. An original method of synthesis of new rare-earth and alkaline-earth element anion-deficient cuprates with a perovskite structure by selective doping of cationic sites (replacement of some copper cations by other elements) has been elaborated in the Laboratory. It was established for the first time that a doping cation occupies preferably octahedral structural sites when it replaces copper cations. As a result, distortion of the octahedra decreases and the new compound is stabilized. We were the first to synthesize and examine the new variable-composition complex oxides of the general formula LaCu_1-xNi_xO_2,5+d, which exhibit a metal-semiconductor phase transition and sharp variation in the oxygen content in air at 500°С, as well as cuprates Ln_8-xA_xCu_8-yM_yO₂₀ (8-8-20), Ln₄BaCu_5-yM_yO_13+d (1-4-5) (Ln=Pr,Nd; A=Ca,Sr; M=Fe,Co,Ni,Ga,Mn), and La₄Sr₄Cu_8-yM_yO₁₈ (8-8-18; M=Ni,Co). While the 8-8-20 and 1-4-5 phases have structures similar those of the familiar cuprates La_8-xSr_xCu₈O₂₀ and La₄BaCu₅O₁₃, the latter oxides were found to have a new unusual crystal structure characterized by binary structural ordering both in the oxygen and metal sublattices. The synthesized cuprates have advanced conducting properties, which are superior to analogous characteristics of high-temperature superconducting cuprates at room temperature.

  
  

  2.  Synthesis and magnetic properties of quasi-one-dimensional complex oxides of the family A_3n+3A’_-n Mn_n+3O_6n+9. We were the first to obtain a new family of quasi-one-dimensional complex manganese oxides of the composition A_3n+3A’Mn_n+3O_6n+9 (A = Ca, Sr, Ba; A’ = Cu, Ni, Co, Mg, Zn), which are structurally related to platinum-metal-based oxides intensively studied in 1990ies. A characteristic feature of the structure of these compounds is the presence of infinite chains composed of octahedra with manganese cations inside and trigonal prisms with bivalent A’ cations alternating in a certain ratio. The chains are separated from each other by alkaline-earth elements. This determines the quiasi-one-dimensional character of the structure of these oxides. The crystal structure of Ca₃A’MnO₆ (n=1) compounds has been refined. As distinct from the oxides with A’= Ni, Co, Zn, which have hexagonal unit cells, Ca₃CuMnO₆ has a triclinic structure. The presence of transition metals in the chains explains the magnetic properties typical of low-dimensional structures, namely, low temperatures of transition to magnetically ordered state. Along with antiferromagnetic oxides, also ferromagnetic oxides have been found.

  
  

  3.  Highly dispersed powders and films of complex vanadium oxides with a layered structure. Powders and films of polyvanadatomybdate xerogels of the general formula M₂V_12-yMo_yO_31-d nH₂O, where M is a univalent cation, having a layered structure, have been obtained for the first time. The ionic state of the elements and partial thermodynamic characteristics of hydrogen and lithium in the structure of these compounds have been determined. The charge carriers in the film specimen were found to exhibit strong mobility anisotropy. A switching phenomenon was found in thin layers of polyvanadates, which were subjected to electrical forming. The films have either electronic or ionic conductivity depending on their composition. The sensory properties of the films can be used in producing highly sensitive resistive transducers of water and ethanol vapor concentration. The compounds exhibit high proton and lithium conductivity, which is comparable with solid ionic conductors used in electrochemical devices.

  
  

  4.  Method of removal of non-ferrous heavy metal impurities from acidic and alkaline sewage. Chemical and electrochemical methods of removal of non-ferrous heavy metals (As, Cu, Pb, Hg) from acidic and alkaline sewage have been developed in the Laboratory. We have proposed a new composition of the acidic sewage precipitant based on sodium hydrosulfide containing a polysulfide zol of the composition MS_1.29. This precipitant made it possible to increase the precipitation rate and to perform the purification process in continuous mode. For automatic dosage of the precipitant, new highly sensitive electrodes have been developed which control the amount of sulfur ions. The new precipitant and the electrodes have been tested for waste water treatment at the Uralelement works, V. Ufaley, Chelyabinsk region. Alkaline waste water is purified with the coagulator Al₂(OH)₅Cl containing polyacrylamide. The electrochemical method consists in electrochemical coagulation with the use of Al electrodes, in reduction of the sewage pH to 8, and in addition of the coagulator. The content of Al, Ni, Zn, and Pb in the waste water upon treatment corresponds to that in distilled water. We have developed a technology and regulations for designing an area at the Uralelectromed industrial complex for processing of vitriol production arsenic wastes into antiseptics, which protect timber from biological damage.

  
  

  5. Novel nano-structured materials. Novel vanadium-oxide nanotubes VO_2.35(C₂H₃)_0.25 have been synthesized by hydrothermal treatment of V₂O₅^.nH₂O gel with an aqueous solution of polyvinyl alcohol. The tubes are 30-150 nm in diameter and several microns in length. We were the first to obtain nanodispersed wire-like anhydrous oxalates based on two transition metals, which, upon subsequent heating, evolve carbon oxide while retaining their shape and acquire a structure of spinel or whiskers several microns (or tens of microns) in length. The materials show promise as oxidation catalysts and as electrodes in electrochemical processes. The results of morphological studies of the spinel phase obtained by thermolysis of binary salt and by thermal treatment at 500°C are given as an example.

  
  

  6.  TiO_2.5-based composite material. In order to obtain a composite material from hydrated titanium dioxide (HTD) with nano-sized particles, synthesis was performed by controlled precipitation of HTD from hydrochloric acid solutions in the presence of dispersed carbon phase. Analysis of air-dry residua, PMR, and IR spectra, as well as thermal studies allowed us to establish the functional composition of HTD (TiO_1.5OH H₂O). Using raster and electron tunneling microscopy it was found that the structure of HTD on a hard bearer is a three-level system: primary particles are 30-40 nm in size, particles of the second aggregation level range from 500 to 900 nm, and the most large particles have the size of 5-10 μm. The particles of the first level are responsible for enhanced selectivity of the composite during sorption of micro-amounts of II group elements from weakly mineralized solutions.

  
  

  7.  Examination of cyanoferrates. The chemistry of cyanoferrate complexes (CFC) with p elements and of hydrated titanium compounds (HTC) was studied because of their potential applications as analytical reagents, inorganic sorbents, ionic conductors, and precursors for synthesis of molecular magnetic materials. However, in spite of the wide range of objects, some questions in the chemistry of CFC and HTC still remain to be cleared up. Spectroscopic investigation of crystallohydrate and anhydrous forms of cyanoferrates (II), (III) of p elements (Sn, Pb) has been performed. We have established the regular features in the oscillation spectra variation depending on the structure and nature of the outer-sphere cation and the central atom in the hydrate composition, as well as on chemical bonding strength and cation-nitrogen bond population parameters. The possibility of embedding lithium chloride molecules in the structure of the crystallohydrate Sn₂Fe(CN)_6.3H₂O was considered in the sorption experiments.

  
  

  Elaboration of unconventional methods for ultra-high pressure synthesis of solid-phase compounds of different morphology, as well as salt and aqueous salt systems including those in the form of nanotubes, nanowhiskers, nanofibers and nanostripes. 

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