Search results for "electron"
showing 10 items of 24810 documents
Relaxation of polarization in (K0.5Na0.5)(Nb0.93Sb0.07)O3 ferroelectric ceramics modified by BaTiO3
2017
ABSTRACTA study of low-frequency relaxation of polarization in conventionally prepared ceramic compounds of (1-x)(K0.5Na0.5)(Nb0.93Sb0.07)O3+xBaTiO3+0.5mol.%MnO2 (x = 0.02, 0.04) examined over a wide temperature range is reported. Anomalous behavior of the temperature dependence of the coercive field Ec(T) is detected in the temperature range of the orthorhombic to tetragonal phase transition. The observed features of polarization are assigned to dynamics of the domain structure at the temperature range of phase coexistence.
On the mechanics of magnetic fluids with field-induced phase transition: application to Couette flow
2018
The influence of Brownian diffusion and magnetophoresis, which are followed by phase transition, on the characteristics of a stationary plane Couette flow of magnetic fluid in a non-uniform magnetic field is discussed. The phase transition conditions in magnetic fluids are assumed as a natural restriction to the particle concentration increase in a non-uniform magnetic field. Profiles of the particles' concentration are calculated, and dependences of the volume magnetic force and of the viscous force are established. © 2018 Institute of Physics, University of Latvia.
Mixed-Mode Operation of Hybrid Phase-Change Nanophotonic Circuits
2016
Phase change materials (PCMs) are highly attractive for nonvolatile electrical and all-optical memory applications because of unique features such as ultrafast and reversible phase transitions, long-term endurance, and high scalability to nanoscale dimensions. Understanding their transient characteristics upon phase transition in both the electrical and the optical domains is essential for using PCMs in future multifunctional optoelectronic circuits. Here, we use a PCM nanowire embedded into a nanophotonic circuit to study switching dynamics in mixed-mode operation. Evanescent coupling between light traveling along waveguides and a phase-change nanowire enables reversible phase transition b…
Single crystal-like thin films of blue bronze
2021
Abstract Pulsed laser deposition technique was employed to grow thin films of K 0.3 M o O 3 on A l 2 O 3 (1-102) and S r T i O 3 (510) substrates. Structural and imaging characterization revealed good quality films with well oriented grains of few microns in length. Both non-selective (transport) and order-selective (femtosecond pump-probe spectroscopy) probes revealed charge density wave properties that are very close to those of the single crystals. The films exhibit metal-semiconductor phase transition in resistivity, pump-probe data show phase transition at the same temperature as the single crystal and the threshold for the photo-induced phase transition is approximately the same as in…
Two-phase dielectric polar structures in 0.1NBT-0.6ST-0.3PT solid solutions
2018
Abstract In this work we address the peculiarities of the macroscopic responses in ternary 0.1Na0·5Bi0·5TiO3-0.6SrTiO3-0.3PbTiO3 (0.1NBT-0.6ST-0.3PT) solid solutions. These solid solutions exhibit a spontaneous first order relaxor to normal ferroelectric phase transition. The phase transition is accompanied by a broad dielectric relaxation which expands over 10 orders of magnitude in frequency just above the phase transition temperature. The temperature dependence of polarization shows that non-zero net polarization persists above the phase transition temperature. Below the phase transition temperature, it is not possible to describe the temperature dependence of polarization with a power l…
Study of the thermochromic phase transition in CuMo1−xWxO4 solid solutions at the W L3-edge by resonant X-ray emission spectroscopy
2021
Abstract Polycrystalline CuMo 1 − x W x O 4 solid solutions were studied by resonant X-ray emission spectroscopy (RXES) at the W L 3 -edge to follow a variation of the tungsten local atomic and electronic structures across thermochromic phase transition as a function of sample composition and temperature. The experimental results were interpreted using ab initio calculations. The crystal-field splitting parameter Δ for the 5d(W)-states was obtained from the analysis of the RXES plane and was used to evaluate the coordination of tungsten atoms. Temperature-dependent RXES measurements were successfully employed to determine the hysteretic behaviour of the structural phase transition between t…
Dielectric behaviour of BaTi1-xZrxO3ceramics obtained by means of a solid state and mechanochemical synthesis
2016
ABSTRACTIn this study the comparison of dielectric behaviour of BaTi1-xZrxO3 (BTZx) ceramic samples prepared by means of a solid state and mechanochemical synthesis was presented. A single phase of perovskite structure was identified in the samples at room temperature. No significant impurities were detected in an EDS spectrum and the samples had a good stoichiometric ratio. The morphology of the investigated samples was characterized by a scanning electron microscopy (SEM). The investigation of dielectric properties of the BTZx samples within the temperature range from 140 K to 600 K was performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. …
Phase transitions in Na0.5Bi0.5TiO3-(Sr0.7Bi0.2)TiO3-PbTiO3 solid solutions
2016
ABSTRACTIncreasing of Sr0.7Bi0.2TiO3 concentration in Na0.5Bi0.5TiO3-Sr0.7Bi0.2TiO3 solid solutions causes increasing of Bi/Na relation and vacancies in the A-site of perovskite structure. In temperature dependence of dielectric permittivity, such a change of composition is reflected by transforming of the frequency-dependent shoulder into a maximum characteristic for relaxor ferroelectrics and diminishing of the frequency-independent maximum characteristic for Na0.5Bi0.5TiO3. Here changes in behavior of dielectric permittivity and polarization are studied if PbTiO3 is added in a certain concentration range of Na0.5Bi0.5TiO3-Sr0.7Bi0.2TiO3 solid solutions. Changes of the characteristic temp…
Luminescence dynamics of hybrid ZnO nanowire/CdSe quantum dot structures
2016
Colloidal CdSe quantum dots (QDs) functionalized with different organic linker molecules are attached to ZnO nanowires (NWs) to investigate the electron transfer dynamics between dots and wires. After linking the quantum dots to the nanowires, the photo-induced electron transfer (PET) from the QDs into the NWs becomes visible in the PL transients by a decrease of dot luminescence decay time. The different recombination paths inside the QDs and the PET process are discussed in the framework of a rate equation model. Photoconductivity studies confirm the electron transfer by demonstrating a strong enhancement of the wire photocurrent under light irradiation into the dot transition. (© 2016 WI…
Defect-related photoluminescence and photoluminescence excitation as a method to study the excitonic bandgap of AlN epitaxial layers: Experimental an…
2020
We report defect-related photoluminescence (PL) and its vacuum ultraviolet photoluminescence excitation (PLE) spectra of aluminum nitride layers with various layer thicknesses and dislocation densities grown on two different substrates: sapphire and silicon. The defect-related transitions have been distinguished and examined in the emission and excitation spectra investigated under synchrotron radiation. The broad PL bands of two defect levels in the AlN were detected at around 3 eV and 4 eV. In the PLE spectra of these bands, a sharp excitonic peak originating most probably from the A-exciton of AlN was clearly visible. Taking into account the exciton binding energy, the measurements allow…