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In this study, an environmentally friendly sol-gel synthetic approach was used for the preparation of yttrium-doped MgFe

The present study investigates thermally induced crystallization and phase evolution of amorphous calcium phosphate (ACP) partially substituted with Fe3+ ions (M/P = 1.5 : 1). It was demonstrated that the presence of Fe3+ ions radically changes the crystallization behavior of ACP and completely prevents the formation of α-tricalcium phosphate (α-TCP, Ca3(PO4)2), which is the first crystalline phase obtained from non-substituted ACP upon thermal treatment. Surprisingly, calcium deficient hydroxyapatite (CDHA) was obtained instead of α-TCP. Such unusual crystallization behavior was observed with a doping level as low as 0.1 mol% with respect to Ca ions. Moreover, it was shown that the presence of Fe3+ ions significantly reduces the crystallization temperature of ACP, which started already at around 400 °C, whereas pristine ACP crystallizes to α-TCP only at around 600 °C. In the presence of Fe3+ ions β-TCP was also obtained at reduced temperature, compared to the formation from non-substituted ACP. The temperature of the complete conversion of CDHA to β-TCP was found to be dependent on the concentration of Fe3+ ions. The crystallization process and phase evolution were monitored employing thermal analysis, XRD, FTIR, Raman, EPR and Mossbauer spectroscopies.

In this study, solid solutions of (1-x)BaTiO3-xBiMnO3 have been synthesized by an aqueous sol-gel method. It was determined that single-phase compounds can be obtained up to x = 0.6 and with further increase in percentage of BiMnO3 component additional crystal phases were detected. Perovskite crystal structure was determined for all synthesized compounds regardless of chemical composition. Raman spectra of synthesized solid solutions showed gradual change of the shape with an increase of BiMnO3 fraction. It was demonstrated that partial substitution of BaTiO3 by BiMnO3 led to the drastic growth of grains of the end products. Magnetization measurements showed that all BiMnO3-containing samples are characterized by paramagnetic behavior. Clear correlation between magnetization values and composition of the materials was observed, magnetization values increased with increasing of BiMnO3 content in solid solutions.

In this study, the BixLa1−xMnO3+δsolid solutions (xfrom 0 to 0.65) were synthesized using sol–gel combustion method with citric acid as a fuel and complexing agent. It was shown that changes in chemical composition of the materials lead to the evolution of crystal structure, morphology, and magnetic properties. The thermal behavior of precursor gel was investigated by thermogravimetric and differential scanning calorimetry (TG-DSC) measurements. X-ray diffraction (XRD) analysis demonstrated that all samples were monophasic. The Rietveld analysis showed that the structure can be indexed by trigonal or cubic unit cell depending on Bi3+content. Scanning electron microscopy (SEM) was used to evaluate morphological features of the synthesized materials and revealed that Bi3+ions significantly promote growth of the grains. The sol–gel-derived BixLa1−xMnO3+δspecimens were also characterized by FT-IR spectroscopy and magnetization measurements, which showed a clear correlation between magnetic properties and crystal structure of the materials.

In this work, lanthanum and manganese co-substitution effects on different properties of bismuth ferrite solid solutions Bi1-xLaxFe0.85Mn0.15O3 (x from 0 to 1) prepared by a sol-gel synthetic approach have been investigated. It was observed that the structural, morphological, and magnetic properties of obtained specimens are influenced by the amount of introduced La3+ ions. Surprisingly, only the compound with a composition of BiFe0.85Mn0.15O3 was not monophasic, and the presence of neighboring phases was determined from X-ray diffraction analysis and Mössbauer measurements. Structural transitions from orthorhombic to cubic and back to orthorhombic were also observed depending on the La3+ amount. Antiferromagnetic behaviour was observed for all of the samples, with the highest magnetisation values for Bi0.5La0.5Fe0.85Mn0.15O3. Additionally, structural attributes and morphological features were evaluated by Raman spectroscopy and scanning electron microscopy (SEM), respectively.

In this study, the aqueous sol-gel method was employed for the synthesis of (1&minus, x)SrTiO3-xBiMnO3 solid solutions. Powder X-ray diffraction analysis confirmed the formation of single-phase perovskites with a cubic structure up to x = 0.3. A further increase of the BiMnO3 content led to the formation of a negligible amount of neighboring Mn3O4 impurity, along with the major perovskite phase. Infrared (FT-IR) analysis of the synthesized specimens showed gradual spectral change associated with the superposition effect of Mn-O and Ti-O bond lengths. By introducing BiMnO3 into the SrTiO3 crystal structure, the size of the grains increased drastically, which was confirmed by means of scanning electron microscopy. Magnetization studies revealed that all solid solutions containing the BiMnO3 component can be characterized as paramagnetic materials. It was observed that magnetization values clearly correlate with the chemical composition of powders, and the gradual increase of the BiMnO3 content resulted in noticeably higher magnetization values.

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.

A correlation between the crystal structure and magnetic properties of system (1-x)BiFeO$_3$-(x)BaTiO$_3$ with compounds across the morphotropic phase boundary was studied using X-ray and neutron diffraction, magnetometry, and Mossbauer spectroscopy measurements. Increase in the dopants content leads to the structural transition from the rhombohedral phase to the cubic phase via a formation of the two-phase region (0.2 < x < 0.33), wherein the magnetic structure changes from the modulated G-type antiferromagnetic to the collinear antiferromagnetic via a stabilization of the non-collinear antiferromagnetic phase with non-zero remanent magnetization. The value of magnetic moment calculated per iron ion based on the Mossbauer and neutron diffraction data decreases from m = 4.4 mB for the compound with x=0.25 to m=3.2 mB for the compound with x=0.35 testifying a dominance of 3+ oxidation state of the iron ions. Increase in the amount of the cubic phase leads to a reduction in the remanent magnetization from 0.02 emu.g for the compounds with the dominant rhombohedral phase (x < 0.27) down to about 0.001 emu/g for the compounds with dominant cubic structure (x >= 0.27). Rapid decrease in the remanent magnetization observed in the compounds across the phase coexistence region points at no direct correlation between the type of structural distortion and non-zero remanent magnetization, while the oxygen octahedra tilting is the key factor determining the presence of non-zero remanent magnetization.

In the present work, a series of powdered Y1-xGdxFeO3 solid solutions (x from 0 to 1) was prepared by an aqueous sol-gel method. Structural properties of the synthesized species were investigated using powder X-ray diffraction (XRD), Raman and Mossbauer spectroscopies. It was demonstrated that single-phase compounds can be obtained in the whole compositional range between the end members of the series. Raman study revealed a gradual change of the Raman spectra depending on the chemical composition of samples. Room-temperature magnetic properties were shown to be strongly dependent on the ratio of Y3+ and Gd3+ ions in analyzed species. Consistent transition from hysteresis characteristic of YFeO3 to almost linear dependence of magnetization of GdFeO3 was observed with an increase of Gd content in prepared powders. On the other hand, this transition was accompanied by a significant increase of magnetization values.

This work was supported by the European Social Fund under the No. 09.3.3- LMT-K-712 “Development of Competences of Scientists, other Researchers and Students through Practical Research Activities” measure. AK would like to express sincere gratitude for Fellowship administrated by The Japan Society for the Promotion of Science (JSPS). Fellow’s ID No.: L12546. Authors are grateful to R. Vargalis (Vilnius University) for taking SEM images. © 2020. This work is licensed under a CC BY-NC-ND license., In the present work, Fe3+ and Zn2+ co-substituted β-tricalcium phosphate (β-TCP) has been synthesized by wet co-precipitation method. Co-substitution level in the range from 1 to 5 mol% has been studied. Thermal decomposition of as-prepared precipitates was shown to be affected by introducing of foreign ions, decreasing the decomposition temperature of precursor. It was determined that partial substitution of Ca2+ by Fe3+ and Zn2+ ions leads to the change in lattice parameters, which gradually decrease as doping level increases. Lattice distortion was also confirmed by means of Raman spectroscopy, which showed gradual change of the peaks shape in the Raman spectra. Rietveld refinement and electron paramagnetic resonance study confirmed that Fe3+ ions occupy only one Ca crystallographic site until Fe3+ and Zn2+ substitution level reaches 5 mol%. All co-substituted samples revealed paramagnetic behavior, magnetization of powders was determined to be linearly dependent on concentration of Fe3+ ions. Cytotoxicity of the synthesized species was estimated by in vivo assay using zebrafish (Danio rerio) and revealed non-toxic nature of the samples. Preparation of ceramic bodies from the powders was performed, however the results obtained on Vickers hardness of the ceramics did not show improvement in mechanical properties induced by co-substitution.----/ / /---- This is the preprint version of the following article: Lauryna Sinusaite, Anton Popov, Andris Antuzevics, Kestutis Mazeika, Dalis Baltrunas, Jen-Chang Yang, Jiun Lin Horng, Shengfang Shi, Tohru Sekino, Kunio Ishikawa, Aivaras Kareiva, Aleksej Zarkov, Fe and Zn co-substituted beta-tricalcium phosphate (β-TCP): Synthesis, structural, magnetic, mechanical and biological properties, Materials Science and Engineering: C 112, 110918 (2020), https://doi.org/10.1016/j.msec.2020.110918, which has been published in final form at https://www.sciencedirect.com/science/article/abs/pii/S0928493119344285#!. This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving. This work is licensed under a CC BY-NC-ND license., European Social Fund under the No. 09.3.3- LMT-K-712; 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.

The magnetic nanosized rare earth iron garnets (R3Fe5O12, where R=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were prepared by an aqueous sol–gel method. Herein we present, that all these garnets can be obtained by this effective synthesis method simply by changing the temperature of the final annealing. It was also demonstrated, that a different annealing temperature leads to a different particle size distribution of the final product. The SEM analysis results revealed that the smallest particles were formed in the range of 75–130 nm. The phase purity and structure of the rare earth iron garnets were estimated using XRD analysis and Mossbauer spectroscopy. Magnetic properties were determined by magnetization measurements. The relation between the particle size, composition and magnetic properties of the sol-gel derived garnets were also discussed in this study.

Superparamagnetic iron oxide nanoparticles (Nps), composed of magnetite, Fe3O4, or maghemite,r-Fe2O3, core and biocompatible polymer shell, such as dextran or chitozan, have recently found wide applications in magnetic resonance imaging, contrast enhancement and hyperthermia therapy. For different diagnostic and therapeutic applications, current attempt is focusing on the synthesis and biomedical applications of various ferrite Nps, such as CoFe2O4 and MnFe2O4, differing from iron oxide Nps in charge, surface chemistry and magnetic properties. This study is focused on the synthesis of manganese ferrite, MnFe2O4, Nps by most commonly used chemical way pursuing better control of their size, purity and magnetic properties. Co-precipitation syntheses were performed using aqueous alkaline solutions of Mn(II) and Fe(III) salts and NaOH within a wide pH range using various hydrothermal treatment regimes. Different additives, such as citric acid, cysteine, glicine, polyetylene glycol, triethanolamine, chitosan, etc., were tested on purpose to obtain good yield of pure phase and monodispersed Nps with average size of

In this study, BiFe1-xMnxO3 (BiFeMnO; x from 0 to 0.5) solid solutions were prepared by low temperature sol-gel processing. It was demonstrated that structural, magnetic and morphological properties of BiFeMnO samples are dependent on the chemical composition of the synthesized BiFe1-xMnxO3 solid solutions. The thermal behaviour of the Bi–Fe–Mn–O precursor gels was investigated by thermogravimetric and differential scanning calorimetry (TG-DSC) measurements. From X-ray diffraction (XRD) analysis it was observed that monophasic BiFe1-xMnxO3 samples have formed up to 25 mol% of substitution. The Rietveld analysis showed that the structure of BiFeMnO specimens can be indexed by rhombohedral or orthorhombic unit cell depending on Mn3+ content. Scanning electron microscopy (SEM) was used to investigate samples morphology and revealed, that smaller particles form when Mn3+ is present inside the structure. Moreover, magnetic properties of solid solutions were also investigated, and antiferromagnetism and weak ferromagnetism were observed for the samples.

In this study for the synthesis of bismuth iron garnet (Bi3Fe5O12; BIG) powders an aqueous sol-gel processing route has been used. Due to the metastability the Bi3Fe5O12 was mostly prepared in thin films form. Only few studies demonstrated the possibility to prepare bulk single-phase BIG. In the suggested sol-gel processing the bismuth nitrate pentahydrate Bi(NO3)3·5H2O and iron nitrate nonahydrate Fe(NO3)3·9H2O, were used as Bi and Fe starting materials, respectively. The 1,2-ethanediol (EG) and citric acid (CA) were selected as complexing agents to ensure the homogeneity of resulted Bi–Fe–O gels. The synthesis products were characterized by X-ray powder diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Mossbauer spectroscopy. The obtained results clearly showed that the perovskite BiFeO3 (BIP) crystalline phase instead of garnet has formed confirming the ambiguity of previously published results on the synthesis and characterization of bulk Bi3Fe5O12.

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 &deg, 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 M&ouml, ssbauer 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.

The interest in core/shell nanowires (Nws) is stimulated by the importance of fabricating materials possessing unique magnetic, catalytic, or optical properties relative to ones of their bulk parents. Here, the fabrication of a novel design of core−shell SnO@SnO2 Nws via heat treatment of Sn Nws, fully encapsulated inside the pores of alumina matrix, is demonstrated. Under this scenario, densely packed arrays of barbed-shaped Nws, possessing extremely high surface areas, have been fabricated. 119Sn Mossbauer effect spectroscopy, high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FESEM), and X-ray diffraction spectroscopy (XRD) were used to study the morphology and composition of the end-products. In addition, electron energy-loss spectroscopy (EELS) was successfully applied here to detect the ionization edges of tin and oxygen in the core and shell part of single Nw.

PurposeThe purpose of this paper is to investigate the influence of fluor‐oligomeric coat on the mechanical properties of steel surface, as well as the chemical interaction of fluor‐oligomeric films with surface and theoretical‐phenomenological interpretation of structural processes in friction surface.Design/methodology/approachFour groups of specimens were studied: two groups of specimens without any wear tests – initial steel specimen as control version and a specimen which was ten times coated by fluor‐oligomer, and two groups of specimens, which were tribologically tested for one million cycles – without any coating and coated specimens. Closed kinematical profile scheme roller‐roller of steel 45 was chosen for tribological tests. Wear of friction surface after those tests was investigated. The interaction between fluor‐oligomer and iron was studied by means of Mössbauer spectroscopy. The micro‐hardness of matrix was also measured.FindingsAffecting the surface of steel by the fluor‐oligomer and friction produces the complicated processes of carbide decay and formation occur. The mechanisms are found which are related to the weakening of chemical bond in steel during the absorption, to the generation of microscopic ruptures, to the decrease (30‐50 per cent) of the amount of carbides and its increase during the friction (up to 50 per cent). The mechanical effect which causes the regeneration of carbides during friction is revealed. Tribological efficiency of fluor‐oligomeric coats (five times lower wear of coated specimens) is explained by the balance of three processes – the softening of matrix during adsorption, the detention of dislocations, and formation of hard particles in the matrix.Originality/valueThe complex mechanism of the increase of wear resistance is explained by filling of ductile matrix with carbide particles.