The improvement of dye‐sensitized solar cells (DSSCs) performance can be realized by using rare‐earth and Nb‐doped TiO2 mesoporous photoelectrodes. The undoped, Nb‐doped, and rare‐earth‐doped TiO2 mesoscopic layers were prepared using a sol–gel method followed by a hydrothermal treatment. The Nb content was varied from 0.7 to 2.7 mol.%. The samples of complex rare‐earth titanium oxides with fluorite‐like structure containing Nb were synthesized using mechanical activation method. A series of fluorite‐like Sm2[TixNb1–x]2O7 compounds with varied Nb content was synthesized. The structure and morphology of obtained materials were characterized using XRD, SEM, and optical absorption spectroscopy. The prepared TiO2 mesoscopic layers were used for fabrication DSSCs. We have found that the photovoltaic parameters of DSSCs based on TiO2 sensitized with N719 dye, are closely related to the electronic structure of the Nb‐doped TiO2 electrodes. The changes of short circuit current of DSSCs were explained in relation to the electronic structure of the TiO2 electrodes. We have shown that the Nb doping enhances the junctions between neighboring nanoparticles and decreases the bulk electrical resistivity of the TiO2 electrodes. For the TiO2 electrodes doped with Nb the best DSSC performance with the energy conversion efficiency of 9.7% was obtained for Ti0.983Nb0.017O2 compound with 1.7 mol.% of Nb. Thus we have improved the device efficiency by 9% in comparison with the DSSC based on undoped TiO2 electrode. The developed rare‐earth doped compounds SmTiNbO were also used for fabrication and characterization of DSSCs. However, unlike Nb‐doped TiO2 layers, the efficiencies of DSSCs based on Nb‐doped complex rare‐earth titanium oxides were low in comparison with undoped TiO2.

The atomic structure of YBa 2 Cu 3 O y fine crystalline HTSC samples with various average crystal lite sizes ranging from 0.4 to 2 μm and an oxygen concentration y close to the optimal value for super conductivity (y ≈ 6.93) is investigated by the neutron diffraction technique. We have found some effects asso ciated with the redistribution of cations and oxygen atoms and with variations in the positions of atomic layers in the unit cell, which are not observed in macrocrystalline samples. In all probability, these effects appear due to nonequilibrium conditions of synthesis required for obtaining this compound in the fine crystalline state. The results have made it possible to explain the peculiar physical properties of fine crystalline YBa 2 Cu 3 O y samples (in particular, the coexistence of high superconducting transition temperatures T c and noticeably lower values of magnetization in strong magnetic fields for T < T c ). It is shown that a nanoscale structural inhomogeneity exists in fine crystalline YBa 2 Cu 3 O y samples with the optimal oxygen content and changes the fundamental superconducting parameters, viz., the magnetic field penetration depth and the coherence length.

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Polycrystalline high-Tc superconductors (HTSCs) with the composition YBa2Cu2.985 57Fe0.015Oy (y≈6.92, Tc=91–91.5 K) with micron and submicron grain sizes are investigated by the method of gamma resonance (Mössbauer) spectroscopy at temperatures of 293, 91, and 78 K. A correlation is found between the changes of the intensities of the components of the Mössbauer spectra and the mean grain sizes 〈D〉. It is shown that the observed changes in the spectra are caused by an interplane redistribution of oxygen wherein the oxygen content δ in the (CuOδ) planes increases and the lattice parameter c decreases. This effect is greater for smaller mean grain sizes 〈D〉. It is concluded that the observed changes in the anion subsystem of the fine-grained HTSCs as compared to bulk equilibrium samples of YBa2Cu3O6+δ are mainly due to a partial interchange of the Y3+ and Ba2+ cations in them. This interchange may be a result of the nonequilibrium synthesis conditions that must be used to produce HTSCs with micron and submicron grain sizes.

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