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In the present work, the phase conversion of amorphous calcium phosphate (ACP) in different molten chlorides (LiCl, NaCl, KCl, CaCl 2) was investigated in detail. The main synthesis parameters influencing the phase purity and morphological features of the products include the chemical composition of molten salts, the heat treatment temperature and the ACP-to-flux ratio. The selective synthesis of single-phase Ca 5 (PO 4) 3 Cl or Ca 2 PO 4 Cl depends on the content of CaCl 2 in the reaction medium. The morphology control of Ca 5 (PO 4) 3 Cl powders was achieved by varying the KCl/CaCl 2 ratio in the flux, resulting in the formation of the particles of different size and shape. The KCl-rich fluxes led to the formation of relatively small nearly spherical particles, whereas the CaCl 2 -rich fluxes promoted an anisotropic growth of the Ca 5 (PO 4) 3 Cl crystals resulting in the formation of monodispersed hexagonally-shaped microrods. Whereas the anisotropic growth was observed at relatively low temperature (750 °C) the increase of the reaction temperature up to 1200 °C significantly reduced this effect leading to the formation of the particles with obviously low aspect ratio. The phase crystallinity and purity were analyzed using powder X-ray diffraction, FTIR spectroscopy as well as 31P, 35Cl and 1H solid-state NMR. The morphological features and chemical composition of the synthesized products were studied by SEM/EDX analysis. [ABSTRACT FROM AUTHOR]

Yttrium manganite (YMnO3) is a compound belonging to the hexagonal rare earth manganites family, which demonstrates multiferroic properties. This material can be prepared by several synthetic approaches, with the most common one being the solid-state synthesis. In this work, we show a possibility of preparing this material via molten salt synthesis using the NaCl-KCl mixture as the reaction medium and yttrium and manganese nitrates as the starting materials. We demonstrate that, by varying the reaction temperature and the nitrates-to-chlorides ratio, it is feasible to synthesize hexagonally shaped particles of microscopic dimensions. A similar synthesis procedure can be successfully applied for the preparation of other hexagonal manganites—ErMnO3, TmMnO3, and YbMnO3. [ABSTRACT FROM AUTHOR]

In this study, ZnO nanostructures with different types of morphologies and particle sizes were evaluated and applied for the development of an immunosensor. The first material was composed of spherical, polydisperse nanostructures with a particle size in the range of 10–160 nm. The second was made up of more compact rod-like spherical nanostructures with the diameter of these rods in the range of 50–400 nm, and approximately 98% of the particles were in the range of 20–70 nm. The last sample of ZnO was made up of rod-shaped particles with a diameter of 10–80 nm. These ZnO nanostructures were mixed with Nafion solution and drop-casted onto screen-printed carbon electrodes (SPCE), followed by a further immobilization of the prostate-specific antigen (PSA). The affinity interaction of PSA with monoclonal antibodies against PSA (anti-PSA) was evaluated using the differential pulse voltammetry technique. The limit of detection and limit of quantification of anti-PSA were determined as 1.35 nM and 4.08 nM for compact rod-shaped spherical ZnO nanostructures, and 2.36 nM and 7.15 nM for rod-shaped ZnO nanostructures, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the present work, gadolinium substitution effects on the properties of yttrium manganite YxGd1−xMn0.97Fe0.03O3 (x from 0 to 1 with a step of 0.2) synthesized by an aqueous sol–gel method have been investigated. Partial substitution of Mn3+ by 57Fe3+ in the manganite was also performed in order to investigate deeper the structural properties of synthesized compounds applying Mössbauer spectroscopy. It was demonstrated that substitution of Y3+ by Gd3+ ions leads to the changes of structural, magnetic and morphological properties of investigated system. The crystal structure gradually transformed from hexagonal to orthorhombic with an increase of Gd3+ content in the crystal lattice. The mixed phase was obtained when x = 0.6, whereas other compounds were determined to be monophasic. Magnetization measurements revealed paramagnetic behavior of all specimens, however magnetization values were found to be dependent on chemical composition of the samples. Solid solutions with orthorhombic structure revealed higher magnetization values compared to those of hexagonal samples. The highest magnetization was observed for pure GdMn0.97Fe0.03O3. Structural properties were investigated by powder X-ray diffraction, Mössbauer, FTIR and Raman spectroscopies. Morphological features of the synthesized specimens were studied by scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

In this study, solid solutions of (1-x)BaTiO 3 -xBiMnO 3 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 BiMnO 3 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 BiMnO 3 fraction. It was demonstrated that partial substitution of BaTiO 3 by BiMnO 3 led to the drastic growth of grains of the end products. Magnetization measurements showed that all BiMnO 3 -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 BiMnO 3 content in solid solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sol-gel method was applied for the preparation of Bi 1-x Gd x Fe 0.85 Mn 0.15 O 3 solid solutions. • The structural, morphological, and magnetic properties were investigated. • The substitutional level depends very much on the synthesis temperature. • Depending on the chemical composition few different structural regions were observed. • Gd–induced paramagnetic contribution to magnetization is proportional to the amount of Gd3+ ions. In the present work, the influence of annealing temperature and chemical composition on the structural, morphological, and magnetic properties of Bi 1-x Gd x Fe 0.85 Mn 0.15 O 3 solid solutions prepared by sol–gel technique was studied. Structural properties were investigated by X-ray diffraction, Raman, FT-IR, and Mӧssbauer spectroscopies, while morphological features were evaluated by scanning electron microscopy (SEM). The low concentration of Gd3+ ions can be introduced into BiFe 0.85 Mn 0.15 O 3 perovskite structure at 500 °C annealing temperature, while heating at higher temperatures (650 °C and 800 °C) resulted in the formation of products in the whole compositional range (x = 0–1). Depending on the chemical composition few different structural regions were observed for solid solutions annealed at 800 °C, including a trigonal, mixture of orthorhombic and trigonal, and orthorhombic unit cells. Gd–induced paramagnetic contribution to magnetization is proportional to the amount of Gd3+ ions. Magnetic properties were determined to be dependent on the annealing temperature of synthesis product. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the present work, a series of powdered Y 1-x Gd x FeO 3 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 Mössbauer 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 YFeO 3 to almost linear dependence of magnetization of GdFeO 3 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. [Display omitted] • Y 1-x Gd x FeO 3 powders were prepared by an aqueous sol-gel method. • Solid solutions were obtained in the whole compositional range between the end members. • Magnetic properties gradually changed along with chemical composition. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

High-entropy garnet crystal structure compounds with novel chemical compositions (Y 3-x-y-z Ca x Li y Ln z Ga 5-m Al m O 12) (Ln – Ce, Eu, Tb) have been synthesized by an aqueous sol-gel method. The multinary substitution of yttrium by calcium, lithium and lanthanide element (cerium, europium and terbium) effects in these gallium/aluminium garnets have been investigated. The intermediates and synthesized end products were characterized by thermal analysis (TG/DTG/DSC), powder X-ray diffraction analysis (XRD), FT-IR spectroscopy and scanning electron microscopy (SEM). The different effects of multinary substitution with calcium, lithium and lanthanide ions in Y 3-x-y-z Ca x Li y Ln z Ga 5-m Al m O 12 samples in comparison with single-metal substitution cases were determined from the results of XRD analysis. The XRD patterns of these samples clearly showed that single phase cubic structure garnets have been synthesized at low substitutional level of yttrium by calcium, lithium and lanthanide element (cerium, europium and terbium). The luminescent properties of (Y 3-x-y-z Ca x Li y Ln z Ga 5-m Al m O 12) (Ln – Ce, Eu, Tb) garnets were also investigated. • Substituted (Y 3-x-y-z Ca x Li y Ln z Ga 5-m Al m O 12) garnets have been synthesized by sol-gel method. • The substitution effect of the Ce, Eu, Tb lanthanides in mixed-metal garnets was investigated. • The substitutional level depends very much on the nature and amount of introduced elements. • Different effects of multinary substitution with calcium, lithium and lanthanides were observed. • The luminescent properties of novel garnets were also investigated. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet and thermal activation spectroscopies were used to study the nature of intrinsic emission and the mechanisms of the formation of electron and hole trapping centres in irradiated Li2SO4 powders and crystals. The obtained results along with excitation spectra showed that recombination emission at 3.8–4.2 eV and 4.5–5.5 eV occurs when an electron passes from the second and third sub-bands of the valence band formed from the 2p state of oxygen to the conduction band. It has been determined that Li2SO4 electron and hole trapping centres are created when electrons are trapped in the SO42– anionic sites. The holes are localised in the form of SO4 – radicals. The spectral position and intensity of individual emission bands are dependent on the crystallographic arrangement of localised holes. [ABSTRACT FROM AUTHOR]

In this study, BiFe 1-x Mn x O 3 (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 BiFe 1-x Mn x O 3 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 BiFe 1-x Mn x O 3 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. Image 1 • BiFe 1-x Mn x O 3 solid solutions were prepared by low temperature sol-gel processing. • The monophasic BiFe 1-x Mn x O 3 samples have formed up to 25 mol% of substitution of manganese. • The rhombohedral or orthorhombic structure of specimens depends on Mn content. • Smaller particles formed when Mn3+ was present in the structure. • Weak ferromagnetism was observed for the samples containing Mn3+. [ABSTRACT FROM AUTHOR]