Na0.5Bi0.5TiO thin films were grown on heated to 200°С Pt/TiO2/SiO2/Si substrates by ex-situ method with high-frequency (13.56 MHz) magnetron deposition. Thermal treatment of the films was carried out at 650°С, 700°С and 800°С. X-ray diffraction investigations showed the films were poly-crystalline and contained additional phase. In the films annealed at 700°C two dominating conduction mechanisms were observed: ohmic at the fields Е < 8 kV/cm and Schottky emission in the field range of 30 – 70 kV/cm. It is also observed that the increase of the film annealing temperature to 800°С leads to the increase of leakage currents. It is assumed that high values of the leakage currents were attributed to the presence of both structure defects and additional unknown phase.
We report some peculiarities of behavior of domain structure and birefringence ∆n of Na0.5Bi0.5TiO3 crystals. Polarization-optical methods are used to study the domain structure and the birefringence ∆n in temperature interval 25°C÷520°C and axial pressure interval 2.5÷60 bar. Single domain state is achieved by application of axial pressure along [100] and [110] directions at temperature near 500°C. Application of axial pressure ~50 bar along [100] direction leads to switching of the samples into anisotropic single domain state. While application of axial pressure ~0.5 bar along [110] direction results in exposition of visually isotropic state and the state is preserved during a cooling process in temperature interval ~500°C÷240°C. In both cases the anisotropic single domain state is observed at room temperature. It is shown that f axial pressure (2.5÷25 bar) application along [110] direction at room temperature leads to a significant increase of the birefringence. It is supposed that both the peculiarities of Δn behavior and the linear behavior of Δn = f(p) are associated with presence of the nanoregions with various orientations of optical indicatrices and their involvement into the orientation process under the action of axial pressure.
Photorefractive crystals Bi12SiO20 (BSO) are particular interest for applications such as spatial light modulators, image amplification and the like. Some properties are connected to distribution of space charge induced in the crystal both by an applied (or intrinsic) electric field and illumination. Many electrical and optical properties as BSO dependence on density and king of localized states. In these paper the results of study of both photoelectret and thermoelectret state (PES and TES) and intrinsic charge distribution as were are presented.
The work reports some aspects of the effect of applied axial pressure on birefringence in Na 0.5 Bi 0.5 TiO 3 crystals, which have peculiarities of the macroscopic properties in a large extent due to the coexistence of nanoregions of different phases in a wide temperature range. The birefringence ∆n is investigated by the polarization-optical method in temperature range 25-500 °C. The temperature behavior of spontaneous birefringence in single domain crystals is associated with the structure phase transitions and the "isotropization point" and depend on the way used to switch the sample into the single domain state. Also, the influence of axial pressure on ∆n of samples preliminary switched to the single domain state is studied. It is discovered that application of the axial pressure (6.25-16.6 bar) along [100] direction does not show significant changes of birefringence in temperature range 25-500 °C. While the application of axial pressure (2.5-25 bar) along [110] direction leads to exhibition of significant piezo-optical effect. It is supposed that both the presence of polar nanoregions and changes of their orientation make contribution to the piezo-optical effect.
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