Cladding-Pumped Er/Yb-Co-Doped Fiber Amplifier for Multi-Channel Operation

The Institute of Solid State Physics, University of Latvia, as a Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. We express our gratitude to rer. nat. Nicoletta Haarlammert from Fraunhofer Institute for Applied Optics and Precision Engineering IOF for the refractive index measurements of ytterbium/erbium-co-doped fibers. This work is supported by the European Regional Development Fund project No. 1.1.1.1/18/A/068.

Electrochemical performance of Na2FeP2O7/C cathode for sodium-ion batteries in electrolyte with fluoroethylene carbonate additive

Abstract Solution synthesis was used to prepare pristine Na2FeP2O7 and Na2FeP2O7/C composite cathode materials for sodium-ion batteries, using glucose as a carbon source. While the pristine Na2FeP2O7 displays capacity of only 45 mAh/g due to the relatively large grain size, the addition of carbon increases the capacity to up to 92 mAh/g (95% of the theoretical 97 mAh/g capacity) with excellent rate capability, as 44 mAh/g capacity is still retained even at 20 C (1.94 A/g) current. The optimal content of carbon was found to be 4.8%. The initial capacity of 81 mAh/g is fully retained after 500 cycles at 1 C, indicating excellent cycle life. Measurements were carried out in 1 M NaClO4 salt in …

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.

High power impulse magnetron sputtering of Zn/Al target in an Ar and Ar/O2 atmosphere: The study of sputtering process and AZO films

Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2017/4 realised at the Institute of Solid State Physics, University of Latvia is greatly acknowledged.

Antibacterial Activity of Positively and Negatively Charged Hematite (α-Fe2O3) Nanoparticles to Escherichia coli, Staphylococcus aureus and Vibrio fischeri

This research and work has been supported by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 (i.e., “to increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure”) of the Operational Programme “Growth and Employment” (No. 1.1.1.2/VIAA/2/18/331).

Tribovoltaic Device Based on the W/WO3 Schottky Junction Operating through Hot Carrier Extraction

Unraveling the Structure and Properties of Layered and Mixed ReO3–WO3 Thin Films Deposited by Reactive DC Magnetron Sputtering

Tungsten trioxide (WO3) is a well-known electrochromic material with a wide band gap, while rhenium trioxide (ReO3) is a “covalent metal” with an electrical conductivity comparable to that of pure metals. Since both WO3 and ReO3 oxides have perovskite-type structures, the formation of their solid solutions (ReO3–WO3 or RexW1–xO3) can be expected, which may be of significant academic and industrial interest. In this study, layered WO3/ReO3, ReO3/WO3, and mixed ReO3–WO3 thin films were produced by reactive DC magnetron sputtering and subsequent annealing in air at 450 °C. The structure and properties of the films were characterized by X-ray diffraction, optical spectroscopy, Hall conductivity…

The role of structural disorder on luminescence of Eu-doped Na0.5Bi0.5TiO3

A detailed analysis of photoluminescence of Eu-doped Na0.5Bi0.5TiO3 (NBT) is performed using it as a tool for describing the local structure of NBT. The obtained results reveal the low symmetry of the Eu3+ local environment in NBT, as indicated by the observed maximal number of sublevels of the 5D0→7F1 and the 5D0→7F2 luminescence transitions, clearly observed at low temperatures. Approximation of the luminescence spectra by Gaussian peaks provides valuable information about the shift of the involved levels upon change of the excitation wavelength. Variation in the strength of the crystal field in Eu-doped NBT is evaluated. Temperature dependence of the luminescence above room temperature i…

Influence of sintering temperature on microstructure of Na0.5Bi0.5TiO3 ceramics

Abstract Na0.5Bi0.5TiO3 (NBT)-based compositions are among the most promising lead-free ferroelectrics. Although studies of modification of NBT-based compositions’ properties are a hot topic, there has been very little attention paid to their characterization from the standpoint of ceramics and the process of producing them. Here, we report on comprehensive analysis of the influence of sintering temperature across a wide temperature range (1020–1240 °C) on the complete microstructure and chemical content of NBT ceramics produced by solid state sintering, which is dominating in producing of NBT ceramics. Thorough attention is paid to the grain size distribution, porosity, and inhomogeneity. …

Amorphous ultra-wide bandgap ZnOx thin films deposited at cryogenic temperatures

Crystalline wurtzite zinc oxide (w-ZnO) can be used as a wide band gap semiconductor for light emitting devices and for transparent or high temperature electronics. The use of amorphous zinc oxide (a-ZnO) can be an advantage in these applications. In this paper we report on X-ray amorphous a-ZnOx thin films (~500 nm) deposited at cryogenic temperatures by reactive magnetron sputtering. The substrates were cooled by a nitrogen flow through the copper substrate holder during the deposition. The films were characterized by X-ray diffraction (XRD), Raman, infrared, UV-Vis-NIR spectroscopies, and ellipsometry. The a-ZnOx films on glass and Ti substrates were obtained at the substrate holder temp…

The Effect of a Nucleation Layer on Morphology and Grain Size in MOCVD-Grown β-Ga2O3 Thin Films on C-Plane Sapphire

This research is funded by the Latvian Council of Science project “Epitaxial Ga2O3 thin films as ultrawide bandgap topological transparent electrodes for ultraviolet optoelectronics” No. lzp-2020/1-0345. S.O. was supported by the European Union’s Horizon 2020 program, under Grant Agreement No. 856705 (ERA Chair “MATTER”). 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 H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².

Membrane-less amphoteric decoupled water electrolysis using WO 3 and Ni(OH) 2 auxiliary electrodes

This work has been supported by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 “To increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure” of the Operational Programme “Growth and Employment” (No. 1.1.1.2/VIAA/3/19/466). Institute of Solid-State Physics, the University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement no. 739508, project CAMART. 2