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The strongly correlated electron material, vanadium dioxide (VO2), has seen considerable attention and research application in metal-oxide electronics due to its metal-to-insulator transition close to room temperature. Vacuum annealing a V2O5(010) single crystal results in Wadsley phases (VnO2n+1

The structure, phase composition and spectral luminescence properties of single crystal and ceramic specimens of (ZrO

The effect of long-term high-temperature annealing on the phase composition, local crystal structure, and oxygen-ion conductivity of SOFC membranes based on zirconium dioxide solid solutions was studied. Crystals with the composition of (ZrO2)0.99−x(Sc2O3)x(R2O3)0.01 (where x = 0.08–0.1; R-Yb, Y, Tb, Gd) were obtained by the method of directed melt crystallization in a cold crucible. The crystals were annealed in air at a temperature of 1000 °C for 400 h. The phase analysis of the crystals before and after annealing was studied by X-ray diffractometry and Raman spectroscopy. The study of the ionic conductivity of the crystals was carried out by the method of impedance spectroscopy in the temperature range 400–900 °C. It has been shown that when various rare earth cations (Yb, Y, Tb, and Gd) are used, the maximum conductivity is observed for the compositions (ZrO2)0.91(Sc2O3)0.08(Yb2O3)0.01, (ZrO2)0.89(Sc2O3)0.1(Y2O3)0.01, (ZrO2)0.90(Sc2O3)0.09(Tb2O3)0.01, and (ZrO2)0.89(Sc2O3)0.1(Gd2O3)0.01. At the same time, these crystals have a highly symmetrical pseudocubic structure, which is retained even after crystal annealing. At comparable concentrations of Sc2O3, the conductivity of crystals decreases with an increase in the ionic radius of the rare earth cation. The high-temperature degradation of the conductivity is also discussed depending on the type of rare earth oxide and the concentration of scandium oxide.

The structure, phase composition and spectral luminescence properties of single crystal and ceramic specimens of (ZrO2)0.909(Y2O3)0.09(Eu2O3)0.001 solid solutions synthesized using uniaxial compaction and slip casting techniques have been compared. The ceramic specimens have been synthesized from crushed single crystal specimens of similar composition. It has been shown that the crystalline structures of the ceramic and single crystal specimens are identical and cubic. The ceramic specimens synthesized using different methods prove to have close microstructure patterns. The spectral luminescence properties of Eu3+ ions in the (ZrO2)0.909(Y2O3)0.09(Eu2O3)0.001 ceramic specimens are similar to those of the single crystals with similar composition. The (ZrO2)0.909(Y2O3)0.09(Eu2O3)0.001 ceramic specimens prove to have uncontrolled Cr3+:Al2O3 impurities due to the synthesis conditions.

The strongly correlated electron material, vanadium dioxide (VO2), has seen considerable attention and research application in metal-oxide electronics due to its metal-to-insulator transition close to room temperature. Vacuum annealing a V2O5(010) single crystal results in Wadsley phases (VnO2n+1, n > 1) and VO2. The resistance changes by a factor of 20 at 342 K, corresponding to the metal-to-insulator phase transition of VO2. Macroscopic voltage-current measurements with a probe separation on the millimetre scale result in Joule heating-induced resistive switching at extremely low voltages of under a volt. This can reduce the hysteresis and facilitate low temperature operation of VO2 devices, of potential benefit for switching speed and device stability. This is correlated to the low resistance of the system at temperatures below the transition. High-resolution transmission electron microscopy measurements reveal a complex structural relationship between V2O5, VO2 and V6O13 crystallites. Percolation paths incorporating both VO2 and metallic V6O13 are revealed, which can reduce the resistance below the transition and result in exceptionally low voltage resistive switching.

We studied the spectral-luminescent properties of (ZrO2)0.805(Y2O3)0.188(Pr2O3)0.007 and (ZrO2)0.802(Y2O3)0.195(Pr2O3)0.003 crystals grown by directional melt crystallization in a cold skull. Analysis of the absorption spectra of the crystals suggested the presence of Pr3+ and Pr4+ ions. Measurement of the relative intensities of the luminescence bands corresponding to the 3P0 → 3H4,5, 3P0 → 3F2,3,4, 3P1 → 3H5 and 1D2 → 3H4 optical transitions of the Pr3+ ions, and analysis of luminescence extinction kinetics for the 3P0 and 1D2 levels of the Pr3+ ions, suggests the presence of cross-relaxation (1D2 → 1G4) → (3H4 → 3F4) of the Pr3+ ions in the ZrO2-Y2O3-Pr2O3 crystals.

Thermal stability of composite bimetallic wires from five novel microalloyed aluminum alloys with different contents of alloying elements (Zr, Sc, and Hf) is investigated. The alloy workpieces were obtained by induction-casting in a vacuum, preliminary severe plastic deformation, and annealing providing the formation of a uniform microstructure and the nucleation of stabilizing intermetallide Al3(Zr,Sc,Hf) nanoparticles. The wires of 0.26 mm in diameter were obtained by simultaneous deformation of the Al alloy with Cu shell. The bimetallic wires demonstrated high strength and improved thermal stability. After annealing at 450–500 °C, a uniform fine-grained microstructure formed in the wire (the mean grain sizes in the annealed Al wires are 3–5 μm). An increased hardness and strength due to nucleation of the Al3(Sc,Hf) particles was observed. A diffusion of Cu from the shell into the surface layers of the Al wire was observed when heating up to 400–450 °C. The Cu diffusion depth into the annealed Al wire surfaces reached 30–40 μm. The maximum elongation to failure of the wires (20–30%) was achieved after annealing at 350 °C. The maximum values of microhardness (Hv = 500–520 MPa) and of ultimate strength (σb = 195–235 MPa) after annealing at 500 °C were observed for the wires made from the Al alloys alloyed with 0.05–0.1% Sc.