0000000000853565
AUTHOR
K. Kundzins
A comprehensive study of structure and properties of nanocrystalline zinc peroxide
Abstract Nanocrystalline zinc peroxide (nano-ZnO2) was synthesized through a hydrothermal process and comprehensively studied using several experimental techniques. Its crystal structure was characterized by X-ray diffraction, and the average crystallite size of 22 nm was estimated by Rietveld refinement. The temperature-dependent local environment around zinc atoms was reconstructed using reverse Monte Carlo (RMC) analysis from the Zn K-edge X-ray absorption spectra. The indirect band gap of about 4.6 eV was found using optical absorption spectroscopy. Lattice dynamics of nano-ZnO2 was studied by infrared and Raman spectroscopy. In situ Raman measurements indicate the stability of nano-ZnO…
Structure, nanohardness and photoluminescence of ZnO ceramics based on nanopowders
ZnO ceramics obtained from grained powders with different grain size by hot pressing and ceramics from tetrapods nanopowders obtained by press-less sintering have been investigated under identical conditions. Ceramics obtained by hot pressing were optically transparent but were composed of large inhomogeneous grains (d = 8–35 μm) exhibiting a substructure. Decreased values of elastic modulus within a grain and a wide defect-associated ('green') photoluminescence (PL) band at 2.2–2.8 eV in conjunction with a weak excitonic band indicate a high concentration of residual point defects in hot pressed ZnO ceramics. Utilization of more small-grained powders contributes to the formation of more un…
The Effects of 3d Admixtures on Properties of Relaxor PLZT8/65/35 Ceramics
A study of the effects of the 3d dopants Mn, Fe, Co, Ni, and Cu on relaxor behavior and other properties of the ferroelectric PLZT8/65/35(La8) ceramic compound by X-ray diffraction, electron microscopy and other techniques is reported. The complex dielectric permittivity ϵ* = ϵ′-iϵ′′ is measured in the 20–400°C range of temperature at frequencies within the range of 102 – 106 Hz. Essential changes caused by the admixtures in the behavior of dielectric permittivity with frequency and temperature are observed along with changes in the XRD SEM patterns are observed. The mechanisms of the phenomena are discussed.
Phase retrieval of a Kolmogorov phase screen from very sparse data using four binary masks
We investigate experimentally the phase retrieval of a Kolmogorov phase screen from very sparse data by modulating its amplitude with four binary masks and compare the retrieved phase screen to the ground truth measured with a surface profiler. Previously, we have shown in simulations that this kind of modulation can be successfully used for the phase retrieval of a Kolmogorov phase screen. After subtracting the ground truth from the retrieved phase screen, the root-mean-square error decreased from 0.14 µm to 0.10 µm. We conclude that a Kolmogorov phase screen can be recovered using simple modulation and very sparse data.
Deformation behavior and interfacial sliding in carbon/copper nanocomposite films deposited by high power DC magnetron sputtering
Abstract Amorphous carbon–copper nanocomposite films with a carbon content from 7 to 40 at.% have been deposited onto steel, silicon and glass substrates using a high power (> 60 W/cm 2 ) and high-rate DC magnetron sputtering technique. XRD, Raman spectroscopy and TEM results confirm that the deposited films consist of copper nanograins (size
Radiation-induced defects in antiferroelectric thin films
Abstract Radiation effects on highly oriented antiferroelectric (AFE) PbZrO3 (PZ) films with a thickness of approximately 400 nm are investigated in view of their possible application as a temperature sensitive element in a new bolometer system for fusion devices like ITER. The films were prepared by pulsed laser deposition (PLD). The dielectric constant was measured in the frequency range from 1 to 250 kHz in a stepwise cooling mode (∼2 °C min−1) from 400 °C to room temperature before and after irradiation to a fast neutron fluence of 2×1022 m−2 (E>0.1 MeV). After irradiation, the films were annealed in several steps up to ∼400 °C to remove the radiation-induced defects. The results are di…
PLZT laser beam modulator
Abstract Laser beam modulator on transparent electrooptic PLZT ceramics are developed for the use in teaching process in schools and universities. Characteristics of the modulator and its electronic control unit are given.
Growth temperature influence on the GaN nanowires grown by MOVPE technique
GaN nanowires (NWs) were successfully grown by Vapor-Liquid-Solid (VLS) growth mechanism on GaN template using metal-organic vapor phase epitaxy (MOVPE) with diameters ranging from 20 to 200 nm and length up to few microns. The characterization by scanning electron microscopy (SEM) reveals an optimum growth temperature at 790°C and X-ray diffraction (XRD) investigations indicates oriented crystallinity of grown NWs.
<title>Glass to ferroelectric phase transition induced by ac electric field in PbMg<formula><inf><roman>1/3</roman></inf></formula>Nb<formula><inf><roman>2/3</roman></inf></formula>O<formula><inf><roman>3</roman></inf></formula> thin films</title>
The nonlinear dielectric response of epitaxial heterostructures of relaxor ferroelectric PbMg1/3Nb2/3O3 thin films was experimentally studied using digital Fourier analysis. The amplitudes and the phase angles of the dielectric harmonics were determined as a function of temperature and the amplitude of the sinusoidal ac field. The response of the films was reconstructed assuming a linear contribution of the film-electrode interface capacitance. In the films at low amplitudes of ac field, a glass-like behavior was identified by a maximum in the third-order nonlinear dielectric permittivity around the freezing temperature, accompanied by a square field dependence of the amplitudes of the odd …
Nitrogen Adsorption on Graphene Sponges Synthesized by Annealing a Mixture of Nickel and Carbon Powders
The present research has been supported by the National Research Programme for 2014–2017 “Multifunctional Materials and Composites, Photonics and Nanotechnologies”.
Impact of Thermal Treatment on the Surface of Na0.5Bi0.5TiO3-Based Ceramics
This research was funded by the European Regional Development Fund, grant number 1.1.1.2/VIAA/3/19/558. The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme, grant number 739508.
Rare Earth Activated Oxyfluoride Glasses and Glass-Ceramics for Scintillation Applications
Oxyfluoride glasses 49SiO2·6Al2O3·24Li2O·20LaF3 activated with Tb, Ce, Eu have been synthesized and studied. After heating at 580°C and 750°C crystalline phases were obtained. The samples were studied by DTA (Differential thermal analyzer), CL (cathodoluminescence), XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive x-ray spectroscopy) methods. We found out that presence of crystalline phase enhances the CL of Tb activated samples significantly; whereas, the shortest decay time of 0.29 μs has been observed for less intense Ce doped glass sample.
NEUTRON IRRADIATION EFFECTS IN PZ and PZT THIN FILMS
ABSTRACT Neutron irradiation effects on highly oriented antiferroelectric PbZrO3 (PZ) and ferroelectric PbZr0.53Ti0.47O3 (PZT) thin films are investigated in view of their possible application as a temperature sensitive element in a new bolometer system for fusion devices like ITER. All investigated thin films were prepared by a sol-gel technique and by pulsed laser deposition (PLD) respectively. The dielectric properties were investigated in a frequency range from 1 to 250 kHz and at temperatures up to 400°C, prior to and after irradiation to a neutron fluence of 3 * 1022 m−2 (E > 0.1 MeV). After irradiation, the films were anneald in several steps up to 400°C in order to remove the radiat…
Optical Gradient of the Trapezium-Shaped NaNbO[sub 3] Thin Films Studied by Spectroscopic Ellipsometry
thin films were performed in the photon energy range of 1.24–4.96 eV.Effective values of the complex refractive index and thickness nonuniformity, roughness, and depth profile of the real part of therefractive index were evaluated. An increase of the refractive index with increasing of the sample thickness was observed anddiscussed.© 2008 The Electrochemical Society. DOI: 10.1149/1.2965786 All rights reserved.Manuscript submitted May 27, 2008; revised manuscript received July 7, 2008. Published August 19, 2008.
Luminescence properties of zirconia nanocrystals prepared by solar physical vapor deposition
Abstract Zirconia nanocrystals have attracted considerable interest as biolabels, which can be used as probes for medical imaging and biosensor applications. However, zirconia particle agglomeration forms a major limitation to its use for biolabeling. In this backdrop, for the first time, well-separated zirconia nanocrystals were obtained in a Heliotron reactor (PROMES CNRS, France) via the solar physical vapor deposition (SPVD) method. As the raw material target for solar evaporation, zirconia nanopowders obtained via the sol–gel process were used. The luminescence and upconversion luminescence properties of the Sol Gel nanopowders were compared with those of the SPVD nanocrystals. Erbium …
<title>Irradiation effects in lead zirconate thin films</title>
Lead zirconate PbZrO3 (PZ) and PbZr0.53Ti0.47O3 (PZT) sol-gel films with a thickness of up to 1.5 μm were deposited on TiO2/Pt/TiO2/SiO2/Si substrates by spin coating technique and heterostructures of the same composition as well as on Pb0.92La0.08 (Zr0.65Ti0.35)O3 (PLZT-8) (with a thickness of 0.4 μm) were pulse laser deposited (PLD) on Pt/Ti/SiO2/Si. Observation of a typical antiferroelectric (AFE) double hysteresis loop in obtained PZ heterostructures at room temperature was attributed to the superior dielectric strength in case of thin film materials. The thermal behavior of dielectric permittivity e of PZ film reveals a maximum near 225°C on heating and 219°C on cooling. The higher res…
The role of nanopowder particle surfaces and grain boundary defects in the sintering of ZnO ceramics
This work focuses on the characteristics of sintered ZnO ceramics and explores the role of source powder morphology in the process of sintering. The source ZnO powders had grained (d = 100 nm) and tetrapod-like (d=50-100 nm, l=3−10 μm) morphologies, they were compacted and sintered at 1200° C. The results have shown that ceramics sintered from the grained powder exhibit relatively high (8%) porosity at grain boundaries and as cavities within grains, which facilitates brittleness. Photoluminescence spectra for these ceramics besides a narrow exitonic band contain a broad "green" luminescence band attributed to defect states. The second ceramics sintered from the tetrapod-like powder has lowe…
Applicability of a binary amplitude mask for creating correctors of higher-order ocular aberrations in a photoresistive layer
Ocular aberrations can be corrected with wavefront correctors created in a photoresist layer. The simplest type of the mask used in optical lithography is a binary amplitude mask. It is known that such a mask has a periodic hole pattern. The purpose of this research was to assess applicability of a binary amplitude mask for creating ocular wavefront correctors. The photoresist was applied to the substrate by using the dip-coating method. The photoresist layer was illuminated through a mask printed on a transparent film by using a laser printer. The surface of the wavefront correctors was evaluated by aberrometry, scanning electron microscopy and profilometry method. The dip-coating method c…
Holographic recording of surface relief gratings in tolyle-based azobenzene oligomers
Abstract Holographic recording of surface relief gratings (SRG) in tolyle-based azobenzene oligomer films have been carried out at 514.5 nm. It was experimentally studied by spectroscopic and AFM methods. The maximum surface modulation amplitude was 35 nm. SRG formation is explained by the mean-field model and by the photodegradation of chromophores enabling the directional mass transport as the result of trans–cis transformations. The conclusion is made that SRG are stable but the diffraction efficiency (DE) changes are due to the complementary decaying amplitude-phase gratings. Strong polarization dependences of transmitted and reflected DE are found. They are explained by the diffraction…
Studies of radiation defects in cerium, europium and terbium activated oxyfluoride glasses and glass ceramics
Abstract Terbium, cerium and europium activated oxyfluoride glasses and glass ceramics have been studied by thermally stimulated luminescence (TSL) and optical absorption techniques after the X-ray irradiation. A creation of colour centres in oxyfluoride glass matrix and TSL peaks depending on the activator type were observed. LaF 3 and rare earth activators were analysed by SEM–EDS.
Raman, electron microscopy and electrical transport studies of x-ray amorphous Zn-Ir-O thin films deposited by reactive DC magnetron sputtering
Zn-Ir-O thin films on glass and Ti substrates were deposited by reactive DC magnetron sputtering at room temperature. Structural and electrical properties were investigated as a function of iridium concentration in the films. Raman spectrum of Zn-Ir-O (61.5 at.% Ir) resembles the spectrum of rutile IrO2, without any distinct features of wurtzite ZnO structure. SEM images indicated that morphology of the films surface improves with the iridium content. EDX spectroscopy and cross-section SEM images revealed that the films growing process is homogeneous. Crystallites with approximately 2-5 nm size were discovered in the TEM images. Thermally activated conductivity related to the variable range…
Poling Induced Mass Transport in Thin Polymer Films
In this study we report investigation of the polymer film morphology modifications during their corona poling for fabrication of nonlinear optically (NLO) active materials. We demonstrate that at certain poling conditions surface and spatial inhomogeneities in the poled area of the sample appear. Densities of the inhomogeinities depend on the strength of the poling field, the sample temperature during the poling, and the prepoling conditions. Optimization of the poling conditions directed toward avoiding surface modifications enables us to increase the overall observable effective nonlinearity of the sample up to 10 times. To investigate, understand, and eventually explain the formation of …
Optimized Deposition of Graphene Oxide Langmuir-Blodgett Thin Films
Abstract Single sheet graphene (SG) is an innovative transparent material with high electrical and thermal conduction the use of which in transparent electrodes instead of traditional materials improves the performance of optoelectronic devices. In this study, graphene oxide (GO) has been obtained by a modified Hummer`s method followed by an advanced technique of water removal (lyophilisation). The Langmuir-Blodgett (LB) method was applied to transfer GO from suspension to substrate. To optimize the deposition process, as suspending and spreading solvents the benzene and benzene/methanol mixtures were chosen instead of previously studied water suspensions. The number of GO layers in suspens…
Antiferroelectric PbZrO3 thin films: structure, properties and irradiation effects
Abstract Irradiation effects on highly oriented antiferroelectric PbZrO 3 and ferroelectric Pb 0.92 La 0.08 (Zr 0.65 Ti 0.35 )O 3 thin films are investigated being exposed to neutron irradiation up to fluence 2*10 22 m −2 . The higher resistance of antiferroelectric PbZrO 3 thin films as compared to ferroelectric heterostructures to large fluences of neutron irradiation is recognized and discussed. Influence of two factors (structural and charge) was taken into account analysing irradiation effects on materials of different polarization states: ferroelectric PLZT (ceramics and thin films) and antiferroelectric PbZrO 3 films.
Investigation of TiO<sub>2</sub> Ceramic Surface Conductivity Using Conductive Atomic Force Microscopy
Dense TiO2 (rutile) ceramic samples were prepared by sintering compacts of titanium dioxide anatase powder at 1500 °C for 5h. Sintered samples were polished and annealed in vacuum at 1000 °C for 1h. Structural properties of the samples were studied by X-ray diffraction, polarized light and scanning electron microscopy. The surface topography and local electrical conductivity of the samples were investigated by atomic force microscopy technique under atmospheric conditions. Enhanced electrical conductivity was observed at grain boundaries while the polished, vacuum annealed grains surface showed non-homogeneous conductivity.
Effect of Yb3+ doping level on the structure and spectroscopic properties of ZnO optical ceramics
This work was partly supported by the RFBR (Grant 19-03-00855).
Aging and Memory Effects in PLZT 8/65/35 Ceramics Modified with 3d Transition-Metal Ions
The temperature and frequency dependencies of the dielectric susceptibility in relaxor electro-optical PLZT 8/65/35 modified with 3d transition-metal ions (Mn, Fe, Co, Ni) measured to study the aging and memory effects are reported. The studies of aging at room temperature show that 3d admixtures (Me) in PLZT 8/65/35 ceramics at small to medium concentration range (Me < 1.0 wt.%) change the depth of dispersion, the aging amplitude and the temperature range of the memory effect. At admixture concentrations Me →1.0 wt% the aging and memory effect are significantly reduced (or eliminated).The obtained results suggest that aging effects are determined by two substantial acceptor effects of the …
Structure and dielectric properties of Na0.5Bi0.5TiO3-CaTiO3 solid solutions
Despite wide studies of Na0.5Bi0.5TiO3, structure of this material and its connection with the observed physical properties still raise numerous questions due to mutually contradicting results obtained. Here, structure and dielectric properties of poled and unpoled Na0.5Bi0.5TiO3-CaTiO3 solid solutions are studied, projecting the obtained concentration dependence of structure and dielectric properties on pure Na0.5Bi0.5TiO3 as the end member of this material group. X-ray diffraction patterns for Na0.5Bi0.5TiO3-CaTiO3 solid solutions reveal dominating of an orthorhombic Pnma phase, even for the compositions approaching the end composition (Na0.5Bi0.5TiO3), whereas structure of pure Na0.5Bi0.…
Ceramics and Thin Films of Some New Pb(B 3+ ,Nb)TiO 3 -PbTiO 3 Systems
The structure, dielectric, and electromechanical properties of (1 m x )Pb(B 3+ ,Nb)TiO 3 - x PbTiO 3 binary systems (B = Lu, Er, Tb, Ho) are reported. The crystallographic features at the morphotropic phase boundary (MPB) between tetragonal P4mm and pseudo-monoclinic M phases are discussed with respect to electro-mechanical properties. Doping effect (with La 3+ ) on the properties of ceramic samples of pseudobinary Pb(Lu 1/2 Nb 1/2 )O 3 -PbTiO 3 (PLuNT) system has been investigated. Pb(Mg 1/3 Nb 2/3 )-PbTiO 3 (PT) solid solutions were studied under different processing conditions for obtaining ceramics of 100% perovskite structure with sufficient high j T EC ∼ 1 K near room temperature. The…
The strain response of piezoelectric multilayer actuators under combined action of electric field and in-plane uniform load
Abstract The driving field governed strain of lead zirconate titanate piezoelectric multilayer actuators have been made within the 107 N/m2 stress and the 3 · 106 V/m triangle-like upward-down-ward driving voltage. A slow strain component as well as a specific relaxation pattern are detected being additional to the periodic part and attributed to the trapped space charge effects favored by nonuniform electric field of the multilayer.
Comparative Study on Micromechanical Properties of ZnO:Ga and ZnO:In Luminiscent Ceramics
The research has been supported by the Project ERANET RUS_ST#2017-051(Latvia) and #18-52-76002 (Russia). The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework, Program H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.
Modeling of trapped charge effects in ferroelectrics: application to piezoactuators
The strain response of lead zirconate titanate piezoelectric multilayer actuators have been measured up to 10 7 N/m 2 stress and the 3.10 6 V/m periodic unipolar driving voltage. An additional nonstationary strain component is detected. This effect is explained in terms of a simple solution of polarization kinetics specific for unipolar driving voltage. Preliminary experimentally assertions are given for space charge effects which manifest itself in the strain as well as charge plot after removing the mechanical load. It demonstrates that the static load free equilibrium of the actuator is not complete and the charge recently supported by the piezo voltage and then trapped forms a nonunifor…
ZnO – Yb2O3 composite optical ceramics: Synthesis, structure and spectral-luminescent properties
International audience; Zinc oxide optical ceramics containing 0 – 2 wt% ytterbium are prepared byuniaxial hot pressing of commercial oxides at 1150 and 1180 °C. The ceramics have themain crystalline phase of hexagonal wurtzite-type ZnO. Ytterbium ions do not enter theZnO crystals but form a cubic sesquioxide phase of Yb2O3 located at the ZnO grainboundaries. Yb acts as an inhibitor for the ZnO grain growth. The ceramics exhibittransmittance up to 60% in the visible. Their transmission in the infrared is determinedby the free charge carrier absorption. The Yb3+ ions are found in C2 and C3i sites in Yb2O3crystals. Under X-ray excitation, the ceramics exhibit intense luminescence bands in the…
Rare earth doped glass–ceramics containing NaLaF4 nanocrystals
Abstract Oxyfluoride glasses 16Na 2 O–9NaF–5LaF 3 –7Al 2 O 3 –63SiO 2 (mol%) activated with 3% terbium, dysprosium, praseodymium and neodymium fluorides have been prepared and studied by differential thermal analysis, cathodoluminescence, X-ray induced luminescence, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. We found out that the presence of crystalline phase enhances the X-ray induced luminescence intensity. X-ray induced luminescence is the most intense for the sample activated with terbium and treated at 700 °C, whereas the praseodymium and neodymium activated samples have the fastest decay times.
Effects of Mn doping on dielectric properties of ferroelectric relaxor PLZT ceramics
This work has been supported by Latvian state research program IMIS2 .
Thermo-optical studies of NaNbO3thin films
Thermo-optical studies of sodium niobate NaNbO3 (NN) thin films, deposited by the pulsed laser ablation technique on Si/SrRuO3 substrates, were performed by spectroscopic ellipsometry in the temperature range 300-550°C. Optical constants at the room temperature were measured in the spectral range 250-1000 nm. Substantial changes in the refractive index temperature behaviour (taken at λ = 300 nm) were found at temperatures 370, 445, 503, 520, and 532°C, where the first and the last temperatures are the phase transitions P → R and S → T1, respectively. Other temperatures (445, 503, and 520°C) are suggested as the points of some local structural changes in the NN film.
Effect of ozone treatment on the microstructure, chemical composition and sensory quality of apple fruits
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research commissioned by Agricultural services co-operative society ‘AUGL¸ NAMS’ has been conducted within framework ‘The research of fruit storage technologies’ funded by State program ‘Competence Centre for Food in Latvia’.