The influence of thermal processing on microstructure of sol–gel-derived SrSnO<Subscript>3</Subscript> thin films

Polycrystalline SrSnO₃ thin films were fabricated using the aqueous sol–gel process and deposited on the single crystal sapphire (R-Al₂O₃ and C-Al₂O₃) and Si substrates by spin coating technique. Two different processing of thermal treatment was explored to produce SrSnO₃ thin films of different porosity. The XRD analysis showed that polycrystalline films with preferential growth of SrSnO₃ (200) plane were obtained on C-Al₂O₃ substrates, while films deposited on R-Al₂O₃ demonstrated a random polycrystalline growth. FE-SEM analysis revealed that the higher porosity of SrSnO₃ films can be achieved by introducing additional thermal treatment step during the deposition procedure. The UV–Vis reflectance spectroscopy was used to study the effect of porosity on optical properties of the films.     

Surface functionalization of ceramic membranes with 3-aminopropyl groups using the sol-gel method

Planar ceramic Al₂O₃ membranes were functionalized with polysiloxane and polysilsesquioxane layers containing 3-aminopropyl groups using the sol-gel method. SEM images show the formation of polysiloxane or polysilsesquioxane layers on the membrane surfaces with the thickness of 0.35 and 4.4 nm, respectively. Infrared spectroscopy data confirmed the presence of the polysiloxane network and functional groups introduced during the synthesis. Measurements of the contact angles on the membrane surfaces showed that the hydrophilicity of the active layer is practically independent of the type of the structuring agent (tetraethoxysilane or 1,2-bis(triethoxysilyl)ethane), and the introduction of the methyl groups increases the hydrophobicity of the surface layer. According to the filtration studies, all functionalized membranes are capable of retaining Cu(II) ions during filtration of diluted solutions due to the complexation of the amino groups in the selective layer with these ions.     

Synthesis and luminescent properties of novel Ba2−xEuxZr2−yHfySi3O12 phosphor

A series of Eu²⁺ activated luminescent materials according to the composition of Ba_2−xEu_xZr_2−yHf_ySi₃O₁₂ were synthesized using a high temperature solid-state reaction method starting from metal oxides and carbonates. Single phase powders were obtained using two annealing steps and boric acid as a flux. Firstly, starting materials were sintered at 1450 °C for 5 h under CO atmosphere and subsequently annealed at 1200 °C for 5 h under N₂/H₂ (95%/5%) gas flow. All samples were characterized by powder X-ray diffraction (XRD) analysis, thermal quenching (TQ), fluorescence lifetime measurements and photoluminescence (PL) techniques. Moreover, emission colour points, luminous efficacies and quantum efficiencies (QE) were calculated and discussed as a function of Eu²⁺ concentration and Zr/Hf ratio of the host lattice.     

Low temperature synthesis and characterization of strontium stannate–titanate ceramics

A novel modified chimie douce synthetic approach based on the gel to crystallite conversion (G–C) method has been developed to prepare strontium titanate SrTiO₃, strontium stannate SrSnO₃, and mixed strontium stannate–titanate SrSn_1−xTi_xO₃ (x = 0.05–0.5). The obtained materials were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The formation of fully crystalline SrTiO₃ was observed in the temperature range of 800–1000 °C. The formation of monophasic SrSnO₃ occurs in the temperature range of 700–900 °C. At lower and higher temperatures the formation an impurity phases such as SrCO₃ and SnO₂ takes place. The same synthetic approach has been applied for the preparation of mixed strontium stannates–titanates SrSn_1−xTi_xO₃. The SEM images of SrTiO₃ samples indicated that the powder particles are 1–5 μm in size having approximately plate-like shape. Quite different surface morphology was determined for SrSnO₃ samples revealing the size of crystals from 500 nm to 40 μm. For the composition with x = 0.15, it was observed that the grain growth is uniform and the size of the grains is of the order of ∼2–5 μm.     

Neodymium substitution effects in sol–gel derived Y3−xNdxAl5O12

Yttrium aluminium garnet (YAG) powders substituted by neodymium Y_3−xNd_xAl₅O₁₂ (x = 0.1, 0.25, 0.35, 0.5, 0.6, 0.7, 0.8, 1.5, 2.0, 2.5, and 3.0) were prepared by a simple aqueous sol–gel method using aluminium nitrate nonahydrate, yttrium oxide, neodymium oxide as the starting materials and ethane-1,2-diol as complexing agent. The powders annealed at 1000 °C in air were characterized by X-ray diffraction (XRD) analysis, infrared (IR) spectroscopy and scanning electron microscopy (SEM). It was demonstrated, however, that the total substitution of yttrium by neodymium does not proceed in the YAG. Pure cubic garnet phase was formed only at low concentration of neodymium (x = 0.1, 0.25, 0.35, 0.5, 0.6, 0.7, 0.8 and 1.5). With further substitution, when the amount of neodymium was x = 2.0, 2.5 and 3.0 the main part of garnet phase transformed in to the perovskite neodymium aluminate (NdAlO₃) phase.     

Synthesis and optical properties of green to orange tunable garnet phosphors for pcLEDs

Y_3−xLu_xAl₃MgSiO₁₂:Ce³⁺ phosphors were prepared by aqueous sol-gel technique. Samples with 0.25, 0.5, 0.75 and 1 mol-% of Ce³⁺ were fabricated and characterized by powder X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and temperature dependent luminescence to reveal the thermal quenching. Moreover, luminous efficacies (LE), CIE 1931 color points and quantum efficiencies (QE) were calculated and discussed. XRD patterns confirmed the presence of single phase garnet for all samples independent of Ce³⁺ concentration and Y/Lu ratio. Phosphors showed broad band emission in the range 500-750 nm. The emission maximum shifts from 555 to 585 nm depending on the Ce³⁺ concentration and Y/Lu ratio. Quantum efficiency of the phosphors decreased with rising Ce³⁺ concentration and increased with increasing Lu content.     

Effect of Mn doping on hydrolysis of low-temperature synthesized metastable alpha-tricalcium phosphate

In the present work, effect of Mn doping on hydrolysis rate of low-temperature synthesized metastable α-tricalcium phosphate (α-TCP) was investigated. α-TCP powders containing different amount of Mn²⁺ ions (0, 0.5 and 1 mol%) were synthesized by wet co-precipitation process, followed by annealing and crystallization of as-precipitated amorphous calcium phosphate at 700 °C. It was demonstrated that the presence of Mn²⁺ ions significantly retards hydrolysis rate of α-TCP. While pristine α-TCP fully hydrolyzed with a conversion to calcium-deficient hydroxyapatite in 10 h, complete hydrolysis of α-TCP doped with 0.5 and 1 mol% of Mn occurred only after 20 and 35 h, respectively. Initial and final products were characterized by X-ray diffraction (XRD) analysis, infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Chemical composition of starting and fully hydrolyzed α-TCP powders was determined by inductively coupled plasma optical emission spectrometry (ICP-OES).     

A novel wet polymeric precipitation synthesis method for monophasic β-TCP

β-Tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP) powders were synthesized using wet polymeric precipitation method for the first time to our best knowledge. The results of X-ray diffraction analysis showed the formation of almost single a Ca-deficient hydroxyapatite (CDHA) phase of a poor crystallinity already at room temperature. With continuously increasing the calcination temperature up to 800 °C the crystalline β-TCP was obtained as the main phase. It was demonstrated that infrared spectroscopy is very effective method to characterize the formation of β-Ca₃(PO₄)₂. The SEM results showed that β-Ca₃(PO₄)₂ solids were homogeneous having a small particle size distribution. The β-TCP powders consisted of spherical particles varying in size from 100 to 300 nm. Fabricated β-TCP specimens were placed to the bones of the rats and maintained for 1–2 months. The histological properties of these samples will be also investigated.     

The study of preparation and photoelectrical properties of chemical bath deposited Zn,Sb and Ni-doped CuInS2 films for hydrogen production

Pure and Zn, Sb, Ni-doped CuInS₂ films were prepared by chemical bath deposition method. Structural, morphological, optical, and photoelectrochemical properties of the as-grown films were investigated. X-ray diffraction analysis revealed that films consisted of the tetragonal CuInS₂ phase. The energy band gaps and carrier densities of these samples were in the ranges of 1.48–1.54 eV and 2.38 × 10¹⁸–9.38 × 10¹⁹, respectively. The maximum photocurrent density of samples with a potential of ?1.0 V vs. a Pt electrode was found to be ?8.58 mA/cm² with the largest hydrogen production capability of 33.26 μmol/cm² under illumination using a 300 W Xe lamp system.