Physicochemical and optical properties of glasses in the Ga4Ge21S50-Sb2S3 system

This paper reports on the results of an investigation into the influence of Sb₂S₃ dopants on the glass-forming ability, heat resistance, softening temperature, density, refractive index, transparent region, and impurity optical absorption of glasses of the composition 0.16GaS₂ · 0.84GeS₂. The data obtained indicate that glasses in the Ga₄Ge₂₁S₅₀-Sb₂S₃ system with a high Sb₂S₃ content are of interest as materials for use in fiber optics.     

Microwave hybrid sintering of 0.95(Mg0.95Zn0.05)TiO3-0.05CaTiO3 ceramics and its microwave dielectric properties

Microwave dielectric ceramic powder of 0.95(Mg_0.95Zn_0.05)TiO₃-0.05CaTiO₃ (MCT) has been prepared by solid-state reaction method through single-step calcination at 1150 °C. The green bodies prepared from the calcined powder have been sintered by conventional, susceptor-aided, and hybrid microwave sintering techniques followed by annealing. XRD of calcined and sintered ceramics show (Mg,Zn)TiO₃ as a major phase with CaTiO₃ as a minor secondary phase. Fractographs of fired ceramics obtained by SEM show similar features in conventional and hybrid microwave types of sintering. Microwave dielectric properties such as relative permittivity(ε_r), temperature coefficient of resonant frequency(τ_f), and unloaded quality factors (Q_u) for conventional sintered at 1325 °C for 4 h are—ε_r~19.8, τ_f< –6 ppm/°C and Q_u.f 69,600 GHz at 6 GHz. Ceramics obtained through susceptor-aided microwave sintering at 1325 °C for 4 h show poor fired density. But ceramics got by microwave-hybrid sintering (resistive + microwave) at the same temperature show ε_r~20.6, Q_u.f~81,600 GHz at 6 GHz and τ_f~?6.9 ppm/°C. The effect of hybrid microwave sintering on the dielectric properties of MCT ceramics is found to be more subtle than microstructural.     

Concentration dependence of the optical properties of glassy alloys in the HgS-Ga2S3-GeS2 system

The concentration dependences of the optical properties of glassy alloys in the HgS-Ga₂S₃-GeS₂ system have been investigated in the spectral range 2.0–2.9 eV. The energy gap E _g of glasses has been estimated, and the dependence of the energy gap on the content of HgS and Ga₂S₃ has been analyzed. The spectral dependences α(hν) for glasses in the system under investigation in the fundamental absorption range are described by the Urbach rule. The alloys containing ≥ 20 mol % (HgS + Ga₂S₃) are characterized by an ordering and a decrease in the energy gap E _g , which are explained by the changes in the short-range order in the arrangement of the atoms involved in the composition of alloys. It has been assumed that, at high concentrations of modifiers, there can arise microscopic inclusions, i.e., different defects, which can scatter light and decrease the transparency of glassy alloys.     

Enhanced permittivity and permeability of (1-y)(Mg0.95Zn0.05)2TiO4-yMg0.95Zn0.05Fe2O4 ceramics

We report the preparation of the solid-solutions (1-y)(Mg_0.95Zn_0.05)₂TiO₄-yMg_0.95Zn_0.05Fe₂O₄ (y = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) by traditional solid-state reaction and systematically study their phases, morphologies, and magnetodielectric properties. The giant dielectric constants are observed at low frequency in the ceramics, with y > 0.5 when the sintering temperature exceeds 1200 $℃$. The highest relative permittivity ${\epsilon }^{\text{'}}$ of 9.98?×?10³ at 30?kHz and the largest squareness ratio of 0.89 for the magnetic hysteresis loop are achieved in 0.1MZT-0.9MZF. In addition, the enhanced initial permeability ${\mu }_i$ of ～70 is obtained in 0.3MZT-0.7MZF due to its large grain size and probably the smaller magnetostriction and internal stress caused by lower relative density. All the results indicate that our solid-solutions with y > 0.5 can considerably improve the dielectric and magnetic properties, providing more advantages than the simple bi-phasic compounds in the applications for novel electronic devices.     

Distribution of Tm3+ and Ni2+ in chalcogenide glass ceramics containing Ga2S3 nanocrystals: Influence on photoluminescence properties

The distribution of Tm³⁺ and Ni²⁺ ions is unambiguously exhibited in 80GeS₂-20Ga₂S₃ chalcogenide glass ceramics (GCs) containing Ga₂S₃ nanocrystals (NCs) by using advanced analytical transmission electron microscopy. Distinctively different distribution patterns of Tm³⁺ and Ni²⁺ ions are observed in the GCs obtained by controlled crystallization. The distribution of the dopants imposes strong influence on their optical properties which are revealed by absorption and photoluminescence (PL) spectra. Detailed discussions are given of the mechanisms of the crystallization-induced PL enhancement and quenching of the Tm³⁺ mid-infrared and Ni²⁺ near-infrared emissions, respectively.     

Antibacterial and photocatalytic behaviour of green synthesis of Zn0.95Ag0.05O nanoparticles using herbal medicine extract

The present work aimed to synthesize Zn_0.95Ag_0.05O (ZnAgO) nanoparticles using rosemary leaf extracts as a green chemistry method. The characterization of Ag-doped ZnO nanoparticles was performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet–visible spectrophotometry (UV–visible). The XRD, FTIR, and UV–visible spectra confirmed the formation of the presence of hexagonal ZnAgO nanoparticles. FESEM micrograph shows that the nanoparticles have been distributed homogeneously and uniformly. The morphology of ZnAgO nanoparticles is quasi-spherical configuration. Also, the mean particle size is in the range of 22–40 nm. The photocatalytic degradation of methylene blue in the presence of Ag-doped ZnO nanoparticles is nearly 98.5% after exposing 100 min. The ultraviolet lamp was used as the light source for photocatalyst degradation. The disc diffusion method was chosen to study the antibacterial activity of as-synthesized ZnAgO nanoparticles. Antibacterial activity of Zn_0.95Ag_0.05O nanoparticles against Staphylococcus aureus and Escherichia coli revealed that the as-synthesized ZnAgO nanoparticles were efficient in inhibition of bacterial growth.     

Influence of glass composition on photoluminescence from Ge2+ or Ag nano-cluster in germanate glasses for white light-emitting diodes

Germanium glass has attracted much interest because of its potential application as the optical waveguides and communication devices. In this work, germanium glass was prepared, exhibiting the blue luminescence at the 410 nm from the Ge²⁺. The influence of SiO₂ addition in the germanate glass on the 410 nm luminescence of the Ge²⁺ was observed. The SiO₂ addition promoted the formation of Ge²⁺, which is because the Si⁴⁺ ions can deprive the O²⁻ ions from the Ge⁴⁺ ion caused by the lower optical basicity of Si⁴⁺ ions than Ge⁴⁺ ion. The germanium glasses containing the Ag nano-clusters were prepared using ion-exchange method. The influence of SiO₂ concentration on the size of Ag nano-clusters was observed, which stabilize the size distribution and lead to the miniaturization of Ag nano-clusters. The Ag nano-clusters size dependence of their photoluminescence was observed in germanate glasses, and the tunable photoluminescence of Ag nano-clusters was obtained by controlling the size of Ag nano-clusters. It is noticed that the Ag nano-clusters formed in the germanate glass showed the white light emission characteristic excited at the blue chip, exhibiting the practical application as the blue converted white light-emitting diodes.     

CaTiO3对Pb0.95Ba0.05Nb2O6压电陶瓷性能的影响

采用标准电子陶瓷工艺制备了(1-x)Pb0.95Ba0.05Nb2O6-xCa0.5TiO3(x=0.01,0.02,0.03,0.04)高温压电陶瓷,研究了CaTiO3对Pb0.95Ba0.05Nb2O6陶瓷的显微组织、相结构,介电和压电性能的影响,得到了CaTiO3掺杂量与Pb0.95Ba0.05Nb2O6陶瓷性能之间的关系.X射线衍射(XRD)分析表明,CaTiO3的加入使Pb0.95Ba0.05Nb2O6很容易形成正交铁电相,而且相同方法制备纯的PbNb2O6是菱方非铁电相钨青铜结构,随着CaTiO3含量的增加,晶胞体积减小.介电温谱测试表明该改性材料具有高居里温度(Tc＞550℃).测试了不同组成陶瓷的压电性能及其热稳定性,当CaTiO3的掺人量x=0.03时,得到压电常数达到d33=69pC/N、平面机电耦合系数Kp=0.30、机械品质因子Qm=27.8、居里温度Tc=570℃的陶瓷样品,该组成具有优异的热稳定性,适合于高温(500℃)环境下使用.     

Enhanced pyroelectric figure of merits of porous BaSn0.05Ti0.95O3 ceramics

Porous BaSn_0.05Ti_0.95O₃ (BTS) ceramics were prepared by sintering compacts consisting of BTS and Poly (methyl methacrylate)(PMMA)as pore former. Porous BTS ceramics were systematically characterized for microstructural, ferroelectric, dielectric and pyroelectric properties. Porosity increased from 4% to 22.5% with increasing PMMA content. Dielectric constant decreases and loss increases with porosity. At 22.5% porosity, relative dielectric constant of BTS decreased by 47% (from 2525 to 1335) at 1 MHz/303K. Porosity leads to significant reduction in dielectric constant and volume specific heat capacity, which are of great interest for improving pyroelectric figure of merits (FOMs). Further, FOMs for current responsivity (F_i), voltage responsivity (F_v), detectivity (F_d) and energy harvesting (F_e and F_e^*) are calculated. Compared with dense ceramic, 2% PMMA specimen showed an improvement of F_e by 166% and F_e^*by 177%. F_v increased by 77%, F_d by 73% and F_i by 56% at 303K. All of these advancements are favorable for pyroelectric device applications.     

Structural, electronic and magnetic properties of Sn0.95Ni0.05O2 nanorods

With a view to investigate the structural, electronic and magnetic properties of Ni (5%) doped SnO(2) diluted magnetic semiconductor nanorods prepared by a PEG-6000 assisted wet chemical route, a systematic investigation has been carried out. The micro structural properties were investigated by Rietveld refinement of XRD data, AFM, TEM, EDS, SAED, FTIR, Raman scattering and XPS measurements. These studies revealed that Sn0.95Ni0.05O2 nanorods have a polycrystalline single phase tetragonal rutile structure without any detectable impurity phases and the aspect ratios of the nanorods are in the range 2.85-10.2. The deconvoluted XPS core level Ni 2p spectral studies determined the oxidation state of Ni as +2. The nanosize effects and local defects are found to influence the local electronic structure of materials. From M-H, M-T, magnetic force microscopy (MFM) and ESR studies, all the samples are found to exhibit clear room temperature ferromagnetism without any metallic clusters. The magnetization behaviour is found to depend on the overlap of percolated bound magnetic polarons and their interactions with dopant induced defects. The magnetic exchange interactions are found to depend on the aggregation behaviour of nanorods, exchange media, the surface diffusion behaviour of randomly distributed Ni ions and the modification of electronic structure.     

Yb3+/Ho3+共掺Ge25Ga5S70玻璃中红外发光特性

用熔融急冷法制备了系列Yb3+/Ho3+共掺Ge25Ga5S70硫系玻璃,测试了样品的吸收光谱以及980nm激光泵浦下中红外荧光光谱特性,用Judd–Ofelt理论计算分析了单掺Ho3+在Ge25Ga5S70玻璃中的强度参数Ωi(i=2,4,6)、自发辐射跃迁几率、荧光分支比和辐射寿命等光谱参数。研究了Yb3+/Ho3+共掺样品在980nm激光泵浦下获得的Ho3+:2.9μm中红外荧光光谱性质,表明Yb3+/Ho3+之间存在能量共振转移。当固定Yb3+掺杂浓度为0.5%(质量分数,下同),随着Ho3+掺杂浓度从0增加为0.7%,Yb3+:2F5/2能级寿命明显单调下降,说明Yb3+/Ho3+之间有效的能量传递主要来源于Yb3+:2F5/2能级向Ho3+:5I6能级的共振能量传递。运用Futchbauer-Ladenburg公式计算比较了不同掺杂浓度下Ho3+:5I6→5I7跃迁的受激发射截面。     

Luminescence of oxide ceramics in the Bi2O3-Er2O3-CeO2 system

The method of pulse high-current cathode luminescence is used to study the Bi₂O₃-Er₂O₃-CeO₂ system at room temperature in air. New luminescence centers associated presumably with cation vacancies and an anion vacancy are determined in systems containing CeO₂. The luminescence parameters are shown to behave nonmonotonically with variation of the composition of the system. It is assumed that an abrupt change in these parameters at a certain composition of the substance corresponds to a phase transformation.     

Optical absorption and selective thermal emission in directionally solidified Al2O3-Er3Al5O12 and Al2O3-Er3Al5O12-ZrO2 eutectics

Al₂O₃-Er₃Al₅O₁₂ and Al₂O₃-Er₃Al₅O₁₂-ZrO₂ eutectic ceramic rods were directionally solidified using the laser floating zone technique at several growth rates. Binary eutectic microstructure consisted in a three-dimensional interpenetrated network of the eutectic phases whereas the ternary eutectic showed a geometrical microstructure at low growth rates and a nanofibrillar pattern at high rates. The microstructure size was strongly dependent on the growth rate, decreasing when the processing rate increased. The optical absorption was measured in the samples at room temperature and Judd–Ofelt analysis was used to model the optical absorption of the Er³⁺ ions. Thermal emission of the eutectic rods was studied at temperatures up to 1600 °C. An intense narrow emission band at 1.55 μm matching with the sensitive region of the GaSb photoconverter was obtained. The intensity of the selective emission band is larger for the binary eutectic than for the ternary compound and increases as the microstructural size decreases.     

Vitreous films of Ga6Ge17S43 composition as a biochip substrate

Adhesion of protein materials with fluorescent stains to the film of Ga₆Ge₁₇S₄₃ composition fabricated by the pulsed laser deposition was investigated. Resistance of the protein markers deposited onto the film to a washing in buffer isotonic solution was established. The obtained results provide the possibility to use these films for the development of protein biochips.     

BaCu(B_2O_5)助烧对0.95MgTiO_3-0.05CaTiO_3微波介质陶瓷性能的影响

研究了BaCu(B2O5)的掺入对0.95MgTiO3-0.05CaTiO3微波介质陶瓷介电性能的影响。用XRD和SEM分析其相组成及微观形貌。结果表明:BaCu(B2O5)的加入能够使0.95MgTiO3-0.05CaTiO3陶瓷的烧结温度降至1100℃并有效抑制第二相MgTi2O5的形成。在1100℃烧结3h,加入3wt%BaCu(B2O5)的0.95MgTiO3-0.05CaTiO3陶瓷获得了较好的介电性能:εr=22.9,Q×f=25,000GHz(7GHz),τf=-3.3ppm/℃(7GHz)。     

Dielectric properties of (Ba0.95Ca0.05)(Ti1-yCay)O3-y ceramics

Calcium doped barium titanate ceramics with composition (Ba_0.95Ca_{0. 05}) (Ti_1-yCa_y)O_3-y prepared by a liquid mixing technique were used to measure the dielectric properties. The pure barium titanate and lightly-Ca-doped materials obey a Curie Weiss law when the temperature is above the Curie temperature. It has been found that the average cubic-tetragonal phase transition temperature moves downward when the octahedrally-coordinated Ca concentration increases, and heavily-Ca-doped barium titanate ceramics show relaxor behavior with a diffuse phase transition characteristic (DPT). Above the average transition temperature T_av the dielectric properties for heavily doped materials do not obey the Curie Weiss law, but can be described by a quadratic relation over a wide range of temperature. Experiments have shown that there exists an extra K(T) peak attributable to the existence of separate microregions of Ba_0.95Ca_0.05TiO₃ in a matrix of (Ba_0.95Ca_0.05) (Ti_1-yCa_y)O_3-y (where y ≤ 2%).     

Enhanced Room Temperature Multiferroic Properties of (Bi0.95La0.05)(Fe0.97Mn0.03)O3/CoFe2O4 and CoFe2O4/(Bi0.95La0.05)(Fe0.97Mn0.03)O3 Double‐Layered Thin Films

Multiferroic (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/CoFe₂O₄ and CoFe₂O₄/(Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃ double‐layered thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates via a chemical solution deposition method. In both the thin films, superior multiferroic properties were observed at room temperature. However, substantial enhancements in magnetic properties, such as saturated ferromagnetic hysteresis loop with large 2M_r (68.8 emu/cm³) and 2H_c (11.7 kOe), as well as moderate ferroelectric properties, such as 2P_r (58 μC/cm²) with low leakage current density (4 × 10^?9 A/cm² at 100 kV/cm), were observed in the (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/CoFe₂O₄ at room temperature. Structural distortion, deformation of [(Fe, Mn)O₆] oxygen octahedra, and superexchange interaction in the (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃ are attributed to the enhanced properties.     

Effects of Mn,Cl co-doping on the structure and photoluminescence properties of novel walnut-shape MAPb0.95Mn0.05I3-xClx films

The novel walnut shape MAPb_0.95Mn_0.05I_3-xCl_x film was successfully synthesized by a one-step method followed by chlorobenzene anti-solvent treatment. The bandgap energy and PL intensity of perovskite film can be effectively tuned by Mn and Cl co-doping. The enlarged bandgap energy is mainly attributed to the synergistic effect of strengthened Pb-I interaction, Cl incorporation and smaller electronegativity of Mn dopants. The stronger coupling between the Mn d- and Pb p-bands, extended carriers diffusion length and more emitting defect-associated states caused by Mn and Cl co-doping are the main reasons for the enhancing PL intensity of MAPb_0.95Mn_0.05I_3-xCl_x walnut shape film. This work not only helps to in-depth understand the correlation between co-doping elements and optical properties of nanostructured perovskite films, but also provides important strategy for future designing the lower-toxic nanostructured perovskite materials with enhanced electrical and optical properties.     

La0.75K0.25Mn0.95Cu0.05O3/CeO2催化净化FCC再生烟气的研究

采用浸渍法制备La0.75K0.25Mn0.95Cu0.05O3/CeO2钙钛矿型复合氧化物催化剂(负载质量分数分别为10％、20％、30％、50％和100％),利用XRD、FT - IR及UV - Vis DRS表征手段对制备的催化剂进行表征,以C2 H2为还原剂,考察该氧化催化剂净化FCC再生烟气的性能.结果表明,制备的系列氧化催化剂存在明显的钙钛矿结构,并且La0.75 K0.25 Mn0.95Cu0.05O3/CeO2 (50％)催化剂的氧化活性最高.