Investigation of lanthanum substitution effects in yttrium aluminium garnet: importance of solid state NMR and EPR methods

Copyright © 2020, Springer Science Business Media, LLC, part of Springer NatureIn this study, yttrium aluminium garnet (YAG) specimens in which yttrium was partially substituted by lanthanum Y3-xLaxAl5O12 (YLaAG) were prepared by an aqueous sol-gel method. YLaAG samples were analyzed by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) methods. The presence of Ce3+ ions as an impurity originating from starting material was determined, therefore, luminescence measurements of YLaAG samples were also recorded. It was demonstrated that luminescent properties are strongly dependent on the phase composition of synthesized species. The XRD analysis results showed that only low substitution of yttrium by lanthanum is possible in Y3-xLaxAl5O12 without destroying garnet crystal structure. It was also demonstrated, that solid state NMR and EPR methods are indispensable tools for the explanation of processes and properties observed in the newly synthesized Y3-xLaxAl5O12 compounds. ---- / / / ---- This is the preprint version of the following article: Laurikenas, A., Sakalauskas, D., Marsalka, A. et al. Investigation of lanthanum substitution effects in yttrium aluminium garnet: importance of solid state NMR and EPR methods. J Sol-Gel Sci Technol (2020). https://doi.org/10.1007/s10971-020-05445-2, which has been published in final form at https://link.springer.com/article/10.1007/s10971-020-05445-2. This article may be used for non-commercial purposes in accordance with Springer Terms and Conditions for Sharing and Self-Archiving.This work was supported by a Research grant NEGEMAT (No. S-MIP-19-59) from the Research Council of Lithuania. 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

Synthesis of lead-based 1212 and 3212 superconductors by an aqueous sol-gel method

The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr2(Y,Ca)Cu2O7±x (Pb–1212) and (Pb2,Cu)Sr2(Y,Ca)Cu2O8±x (Pb–3212) superconductors using two different complexing agents, namely 1,2-ethanediol and tartaric acid was studied. The phase transformations, composition and micro-structural features in the polycrystalline samples were studied by powder X-ray diffraction analysis (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XRD analysis of the ceramic samples obtained by calcination of Pb-Sr-Y-Ca-Cu-O acetate-glycolate precursor gels in air, for 10 hours at 800°C and at 825°C, showed the presence of homogeneous Pb–1212 and Pb–3212 crystallites as major phases. The XRD patterns of the ceramics obtained from Pb-Sr-Y-Ca-Cu-O acetate-tartrate precursor gels, however, showed multiphasic character. The critical temperature of superconductivity (TC (onset)) observed by resistivity measurements were found to be 91 K and 75 K for Pb–1212 and Pb–3212 samples, respectively

Sol-gel derived coatings for the conservation of steel

In this paper, sol-gel processing route has been applied and investigated for the conservation of steel. Nanosilica coatings on steel surface have been prepared using tetraethylorthosilicate (TEOS) as a starting material. The methyl-modified silica sols were obtained by mixing of 3 mas.% SiO2 sol solution with hexamethyldisilozane (HMDS). The surface of steel was coated by dip-coating technique. In order to compare the characteristics of coatings, the steel substrates were also coated with commercial polymers Paraloid B67, Cosmolloid H80 and Antik Patina. The surface morphology changes of the uncoated and coated specimens before and after photochemical ageing were investigated by scanning electron microscopy and atomic force microscopy. The structure of the prepared coatings was also investigated by FTIR spectroscopy. The hydrophobicity of surfaces was evaluated by contact angle measurements. Potentiodynamic measurements were obtained in order to compare corrosion parameters of the coatings

Sol-Gel Synthesis and Characterization of Yttrium-Doped MgFe2O4 Spinel

In this study, an environmentally friendly sol-gel synthetic approach was used for the preparation of yttrium-doped MgFe2O4. Two series of compounds with different iron content were synthesized and A-site substitution effects were investigated. In the first series, the iron content was fixed and the charge balance was suggested to be compensated by a partial reduction of Fe3+ to Fe2+ or formation of interstitial O2− ions. For the second series of samples, the iron content was reduced in accordance with the substitution level to compensate for the excess of positive charge, which accumulates due to replacing divalent Mg2+ with trivalent Y3+ ions. Structural, morphological and magnetic properties were inspected. It was observed that single-phase compounds can only form when the substitution level reaches 20 mol% of Y3+ ions and iron content is reduced. The coercivity as well as saturation magnetization decreased with the increase in yttrium content. Mössbauer spectroscopy was used to investigate the iron content in both tetrahedral and octahedral positions

Structure Modification, Evolution, and Compositional Changes of Highly Conductive La:BaSnO3 Thin Films Annealed in Vacuum and Air Atmosphere

Perovskite-type La:BaSnO3 (LBSO) has been drawing considerable attention due to its high electron mobility and optical transparency. Its thin film electrical properties, however, remain inferior to those of single crystals. This work investigates the thermal post-treatment process of films deposited using the metalorganic chemical vapor deposition method to improve the electrical properties of different stoichiometry films, and demonstrates the modification of thin film’s structural properties using short and excessive annealing durations in vacuum conditions. Using vacuum post-treatment, we demonstrate the improvement of electrical properties in Ba-rich, near-stoichiometric, and Sn-rich samples with a maximum electron mobility of 116 cm2V−1s−1 at r.t. However, the improvement of electrical properties causes surface morphology and internal structural changes, which depend on thin film composition. At temperatures of 900 °C–1400 °C the volatile nature of LBSO constituting elements is described, which reveals possible deterioration mechanisms of thin LBSO air. At higher than 1200 °C, LBSO film’s decomposition rate increases exponentially. Thin film structure evolution and previously unreported decomposition is demonstrated by Ba and La diffusion to the substrate, and by evaporation of SnO-SnOx species

Acrylate–gelatin–carbonated hydroxyapatite (cHAP) composites for dental bone-tissue applications

Various types of scaffolds made of synthetic polymers have been widely studied for bone-tissue applications due to their mechanical strength, biocompatibility and biodegradability, but the hydrophobic nature of synthetic polymers and frequent absence of pores within the scaffolds inhibit cellular attachment, infiltration, and tissue ingrowth. In this study, multi-composite scaffolds composed of dipentaerythritol hexa-acrylate (DPHA), ethylene glycol dimethacrylate (EGDMA), gelatin, and carbonated hydroxyapatite (cHAP) have been made. Percentage ratio of polymer matrix to gelatin was varied 50/50, 75/25, and 95/5 to change the porosity of the resultant scaffolds. The structure, crystallinity, and phase composition of the cHAP were confirmed by FTIR, Raman, XRD and Rietveld analyses, TG/DSC was used to evaluate the distribution of ceramics within the polymer matrix, and FTIR-ATR was used to confirm the molecular structure of composites. SEM/EDS analysis of the scaffolds revealed cavities and irregularities in the surface, and that cHAP was indistinctly exposed on the composite surface, computed tomography (CT) was used to estimate the density and homogeneity of the scaffolds, and the cHAP distribution within the scaffolds was evaluated by conventional radiography. The hydrophilicity of the multi-composite scaffolds was investigated using an aqueous solution of methylene blue dye which showed that the acrylate(75%)–gelatin(25%)–cHAP composite had the highest hydrophilicity. The results suggest that acrylate–gelatin–cHAP scaffolds have a potential for bone-tissue engineering. Godkänd;2021;Nivå 0;2021-02-09 (johcin)FORMAS "Utilization of solid inorganic waste from the aquaculture industry as wood reinforcement material for flame retardancy 2018-01198

A Facile Synthesis and Characterization of Highly Crystalline Submicro-Sized BiFeO3

In this study, a highly crystalline bismuth ferrite (BFO) powder was synthesized using a novel, very simple, and cost-effective synthetic approach. It was demonstrated that the optimal annealing temperature for the preparation of highly-pure BFO is 650 °C. At lower or higher temperatures, the formation of neighboring crystal phases was observed. The thermal behavior of BFO precursor gel was investigated by thermogravimetric and differential scanning calorimetry (TG-DSC) measurements. X-ray diffraction (XRD) analysis and Mössbauer spectroscopy were employed for the investigation of structural properties. Scanning electron microscopy (SEM) was used to evaluate morphological features of the synthesized materials. The obtained powders were also characterized by magnetization measurements, which showed antiferromagnetic behavior of BFO powders

Phytochemical and antioxidant profiles of leaves from different <i>Sorbus</i> L. species

<div><p>Leaves of <i>Sorbus</i> L. have been used in various traditional medicine systems. Phenolic compounds determine the main pharmacological effects of <i>Sorbus</i> L. In this study, phytochemical and antioxidant profiles of <i>Sorbus anglica</i>, <i>Sorbus aria</i>, <i>Sorbus arranensis</i>, <i>Sorbus aucuparia</i>, <i>Sorbus austriaca</i>, <i>Sorbus caucasica</i>, <i>Sorbus commixta</i>, <i>Sorbus discolor</i>, <i>Sorbus gracilis</i>, <i>Sorbus hostii</i>, <i>Sorbus semi-incisa</i> and <i>Sorbus tianschanica</i> were determined. Twenty four constituents were identified in <i>Sorbus</i> L. species using ultra high performance liquid chromatography coupled to quadruple and time-of-flight mass spectrometers. Post-column FRAP assay identified compounds with reducing activity and revealed significantly greatest total antioxidant activity of 175.30 μmol TE/g DW, 169.20 μmol TE/g DW and 148.11 μmol TE/g DW in <i>S. commixta</i>, <i>S. discolor</i> and <i>S. gracilis</i> leaf samples, respectively, with neochlorogenic and chlorogenic acids being most significant contributors. Characteristic fingerprints of phytochemical and antioxidant profiles could be applied for the quality evaluation of various raw materials of <i>Sorbus</i> L. species.</p></div