Fabrication and properties of novel low-melting glasses in the ternary system ZnO-Sb2O3-P2O5

Glasses in the ternary system ZnO-Sb₂O₃-P₂O₅ were investigated as potential alternatives to lead based glasses for low temperature applications. The glass-forming region of ZnO-Sb₂O₃-P₂O₅ system has been determined. Structure and properties of the glasses with the composition (60 − x)ZnO-xSb₂O₃-40P₂O₅ were characterized by infrared spectra (IR), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results of IR indicated the role of Sb³⁺ as participant in glass network structure, which was supported by the monotonic and remarkable increase of density (ρ) and molar volume (V_M) with increasing Sb₂O₃ content. Glass transition temperature (T_g) and thermal stability decreased, and coefficient of thermal expansion (α) increased with the substitution of Sb₂O₃ for ZnO in the range of 0-50 mol%. XRD pattern of the heat treated glass containing 30 mol% Sb₂O₃ indicated that the structure of antimony-phosphate becomes dominant. The improved water durability of these glasses is consistent with the replacement of easily hydrated phosphate chains by corrosion resistant P-O-Sb bonds. The glasses containing ?30 mol% Sb₂O₃ possess lower T_g (<400 °C) and better water durability, which could be alternatives to lead based glasses for practical applications with further composition improvement.     

Hydrothermal growth of NiSe2 tubular microcrystals assisted by PVA

NiSe₂ tubular microcrystals assembled of nanoparticles have been prepared via a hydrothermal method in an ethanolamine and water mixed solution assisted by polyvinyl alcohol (PVA). The prepared tubular crystals with hexagonal structure are composed of nanoparticles with average diameter of 30 nm. It was found that the phase of the products could be adjusted by the molar ratio of the reactants (Ni/Se), and the morphology of the products could be greatly influenced by the quantity of surfactant PVA. Based on the experimental results, the possible formation mechanism of NiSe₂ tubular microcrystals is also discussed.     

Glass formation in the Sb2O3-CdCl2-SrCl2 ternary system

Vitreous systems based on antimony oxide Sb₂O₃ have been investigated. The limits for glass formation are reported in the Sb₂O₃-CdCl₂-SrCl₂ ternary system, and in the Sb₂O₃-SrCl₂-(0.5CdCl₂ + 0.5ZnCl₂) pseudo ternary system. Amorphous state is confirmed by XRD patterns. Thermal measurements implemented by differential scanning calorimetry show that Tg is above 300 °C. As a general trend, Tg increases with chloride content. These glasses have an extended transmission in the mid-infrared spectrum with a refractive index larger than 2. The influence of the CdCl₂/Sb₂O₃ substitution on the physical properties has been studied in the (90 − x)Sb₂O₃-xCdCl₂-10SrCl₂ system: thermal expansion, Vickers microhardness, Young and bulk modulus decrease as cadmium concentration increases. An inverse dependence is observed for shear modulus. This behaviour is discussed in relation to structural hypothesis.     

A template‐free route for controlled synthesis of dumbbell‐like Sb2S3 microcrystals

Large amounts of dumbbell‐like Sb₂S₃ microcrystals were synthesized via a simple solvothermal treatment method. Various techniques such as x‐ray diffraction (XRD), field‐emission scanning electron microscope (FESEM), high‐resolution transmission electron microscope (HRTEM), selected area electron diffraction (SAED), and photoluminescence spectrometry (PL) have been used to characterize the obtained products. The results showed that the products belong to the orthorhombic Sb₂S₃ phase, and the dumbbell‐like Sb₂S₃ microcrystals were composed by uniform microrods. Besides, the morphologies of Sb₂S₃ microcrystals could be changed from microshperes to dumbbell‐like microcrystals by only adjusting the reaction solvent. The solvent effects are discussed in detail. Furthermore, the PL properties of the obtained Sb₂S₃ microcrystals clearly show shape effects. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and physical properties of glasses in the Sb2O3-PbCl2-MoO3 system

Lead chloroantimonite glasses form stable binary glasses that may accommodate numerous oxides or halides as a third component. Molybdenum trioxide is a glass progenitor leading to molybdate glasses. Ternary glasses have been synthesized and studied in the Sb₂O₃-PbCl₂-MoO₃ system. Compositional limits of glass formation are reported and two series of glass samples have been prepared corresponding to the general formulas: (90 − x)Sb₂O₃-xPbCl₂-10MoO₃ and (90 − x)Sb₂O₃-xMoO₃-10PbCl₂. Glass transition temperature is close to 290 °C at high Sb₂O₃ content and decreases as antimony oxide is substituted by MoO₃ or PbCl₂. Position, width and intensity of crystallization peak suggest that devitrification rate is small in some composition ranges. The evolution of density, thermal expansion, refractive index and microhardness has been studied as a function of composition parameter x. Deviations from linearity are observed. They suggest structural changes in the case of the MoO₃/Sb₂O₃ substitution while it appears that molar volume increases linearly versus lead content in the other series of glasses. Refractive index is close to 2.04. Optical transmission ranges from 550 nm in the visible spectrum to 5.5 μm in the infrared. It is limited by extrinsic absorption bands arising from hydroxyls and silicon impurities. Young's, bulk and shear moduli have been measured for the two series of samples.     

Electrical and dielectric properties of Sb2O3–V2O5–K2O glasses

Electric measurements, including temperature dependencies of direct electrical conductivity and temperature dependencies of complex electrical modulus, have been implemented using Sb₂O₃–V₂O₅–K₂O glass samples. These glasses absorb ambient humidity but their resistance to water attack depends on composition. The significant decrease of conductivity up to 100 °C can arise from water desorption. Cycling measurements of direct electrical conductivity versus temperature were also implemented. They show that the 30Sb₂O₃–30V₂O₅–40K₂O and 70Sb₂O₃–30K₂O glasses are irreversibly damaged with the formation of the hydrated layer. In addition, it was observed that the evolution of DC conductivity is ruled by Arrhenius relation, while activation energy decreases as Sb₂O₃ concentration increases.     

Density-structure correlations in Na2O-CaO-P2O5-SiO2 bioactive glasses

Relations for Na₂O-CaO-SiO₂ glasses have been developed to calculate the density of Na₂O-CaO-P₂O₅-SiO₂ bioactive glasses. The calculation makes use of NMR results of O’Donnell et al. indicating that P₂O₅ forms a separate phase, containing Na₃PO₄ and Ca₃(PO₄)₂, in the investigated glasses. The volume of the silicate units is the same as that found in Na₂O-CaO-SiO₂, Na₂O-SiO₂, and CaO-SiO₂ glasses. Similarly, the volume of PO₄ units is equivalent to that in Na₃PO₄ and Ca₃(PO₄)₂. Calculated densities are consistent with the experimental data.     

Phase separation and crystallization in the system SiO2-Al2O3-P2O5-B2O3-Na2O glasses

The phase separation and crystallization behavior in the system (80 − X)SiO₂ · X(Al₂O₃ + P₂O₅) · 5B₂O₃ · 15Na₂O (mol%) glasses was investigated. Glasses with X = 20 and 30 phase separated into two phases, one of which is rich in Al₂O₃-P₂O₅-SiO₂ and forms a continuous phase. Glasses containing a larger amount of Al₂O₃-P₂O₅ (X = 40 and 50) readily crystallize and precipitates tridymite type AlPO₄ crystals. It is estimated that the phase separation occurs forming continuous Al₂O₃-P₂O₅-SiO₂ phase at first, and then tridymite type AlPO₄ crystals precipitate and grow in this phase. Highly transparent glass-ceramics comparable to glass can be successfully obtained by controlling heat treatment precisely. The crystal size and percent crystallinity of these transparent glass-ceramics are 20-30 nm and about 50%, respectively.     

Spectroscopic properties of Er-doped Na2O-Sb2O3-B2O3-SiO2 glasses

Spectroscopic properties of Er³⁺-doped Na₂O-Sb₂O₃-B₂O₃-SiO₂ glasses have been investigated for developing 1.5-μm broadband fiber amplifiers. An intense 1.5-μm near infrared emission with a broad full width at half maximum (FWHM) of 88 nm has been obtained for Er³⁺-doped 5Na₂O-20Sb₂O₃-35B₂O₃-40SiO₂ glass upon excitation with a 980 nm laser diode. The obtained emission cross-section of the ⁴I_13/2 → ⁴I_15/2 transition and the lifetime of the ⁴I_13/2 level of Er³⁺ ions are 6.8 × 10⁻²¹ cm² and 0.36 ms, respectively. It is noted that the product of the emission cross-section and the FWHM of the glass, σ_e × FWHM, is as great as 598.4 × 10⁻²¹ cm² nm, which is comparable or higher than that of Er³⁺-doped bismuth-based and tellurite-based glasses. These special optical properties encourage in identifying them as important materials for potential applications in high performance optics and optical communication networks.     

Crystallization processes of Li2O-Ga2O3-SiO2-NiO system glasses

Crystallization processes of Li₂O-Ga₂O₃-SiO₂-NiO system glasses have been studied by X-ray diffraction, differential calorimetry and optical absorption. Transparent glass-ceramic containing LiGa₅O₈:Ni²⁺ as the sole crystalline phase has been obtained from glass with the composition of 13Li₂O-23Ga₂O₃-64SiO₂-0.1NiO (in mol%) by the heat treatment in the temperature range from 923 to 953 K. It was revealed that the specific surface area of samples enhances crystallization of LiGaSi₂O₆ but obstructed that of LiGa₅O₈. LiGa₅O₈ grew to nano-sized crystallites dispersed in the glass matrices and did not affect the transparency seriously. In contrast, LiGaSi₂O₆ grew to crystallites with diameters more than 100 nm on the surface and made the glasses opaque. Optical absorption measurements revealed that doped Ni²⁺ occupied five-folded trigonal bipyramidal sites in the as-quenched glass matrices but six-folded octahedral sites of precipitated LiGa₅O₈ in the glass-ceramics. It was confirmed that transparent glass-ceramic containing Ni²⁺:LiGa₅O₈ was effectively obtained by the heat treatment at a temperature of 953 K for 10 h.     

Thermal-induced phase transition and assembly of hexagonal metastable In2O3 nanocrystals: A new approach to In2O3 functional materials

This paper reports on the thermal-induced performance of hexagonal metastable In₂O₃ nanocrystals involving in phase transition and assembly, with particular emphasis on the assembly for the preparation of functional materials. For In₂O₃ nanocrystals, the metastable phase was found to be thermally unstable and transform to cubic phase when temperature was higher than 600 °C, accompanied by assembly as well as evolution of optical properties, but the two polymorphs coexisted at the temperature ranging from 600 to 900 °C, during which the content of product phase and crystal size gradually increased upon increasing temperature. The assembly of In₂O₃ nanocrystals can be developed to fabricate In₂O₃ functional materials, such as various ceramic materials, or even desired nano- or micro-structures, by using metastable In₂O₃ nanocrystals as precursors or building blocks. The electrical resistivity of In₂O₃ conductive film fabricated by a hot-pressing route was as low as 3.72×10⁻³ Ω cm, close to that of In₂O₃ single crystal, which is important for In₂O₃ that is always used as conductive materials. The findings should be of importance for both the wide applications of In₂O₃ in optical and electronic devices and theoretical investigations on crystal structures.     

Effect of temperature on dielectric properties of SnO2/Sb2O3 mixed thin films

Thin films of various thicknesses in the MIM structure have been prepared from the powder of SnO₂/Sb₂O₃ mixed sample by the thermal evaporation technique in a vacuum of 10⁻⁵ Torr. Dielectric properties of SnO₂/Sb₂O₃ mixed thin films have been studied with temperature starting from LNT to RT and above RT and frequency ranging from 100 Hz to 16 kHz. The activation energy for the migration of charge carriers in SnO₂/Sb₂O₃ mixed thin films has been calculated and it is found to be 0.23 eV. The results thus obtained on dielectric properties of SnO₂/Sb₂O₃ mixed thin films are presented and discussed.     

Capacitance-voltage characteristics of In0.3Ge2Sb2Te5 thin films

The influence of indium doping on the capacitance variation with temperature and applied bias voltage of Ge₂Sb₂Te₅ is investigated. The capacitance-voltage (C-V) measurements of In_0.3Ge₂Sb₂Te₅ and Ge₂Sb₂Te₅ thin films were performed for a sweep of voltages from −20 to +20 V at different temperatures. The results show different capacitance behavior of In_0.3Ge₂Sb₂Te₅ and Ge₂Sb₂Te₅ films. As the temperature increases the capacitance of the indium-doped sample decreases and becomes negative. The negative capacitance effect might be attributed to a significant increase of the film’s conductivity due to temperature and applied bias voltage. The nonlinearity in the capacitance and conductivity could be related to the nucleation mechanism as the temperature becomes close to the amorphous-crystalline transition temperature.     

Laser-induced crystallization of β′-RE2(MoO4)3 ferroelectrics (RE: Sm, Gd, Dy) in glasses and their surface morphologies

The glasses with the compositions of 21.25RE₂O₃-63.75MoO₃-15B₂O₃ (RE: Sm, Gd, Dy) were prepared and the formation of β′-RE₂(MoO₄)₃ ferroelectrics was confirmed in the crystallized glasses obtained through a conventional crystallization in an electric furnace. The features of the glass structure and crystallization behavior were clarified from measurements of Raman scattering spectra. Continuous-wave Nd:YAG laser with a wavelength of 1064 nm (laser power: 0.6-0.9 W, laser scanning speed: S = 1-16 μm/s) was irradiated to 10.625Sm₂O₃-10.625Gd₂O₃ (or Dy₂O₃)-63.75MoO₃-15B₂O₃ glasses, and the structural modification was induced at the glass surface. At the scanning speed of S = 10 μm/s, crystal lines consisting of β′-Gd_2−xSm_x(MoO₄)₃ or β′-Dy_2−xSm_x(MoO₄)₃ crystals were patterned on the glass surface. It was found that those crystal lines have the surface morphology with periodic bumps. At S = 1 μm/s, it was found that crystal lines consist of the mixture of paraelectric α-Gd_2−xSm_x(MoO₄)₃ and ferroelectric β′-Gd_2−xSm_x(MoO₄)₃ crystals, indicating the phase transformation from the β′ phase to the α phase during laser irradiation. Homogeneous crystal lines with β′-RE₂(MoO₄)₃ ferroelectrics have not been written in this study, but further research is continuing.     

Facile synthesis and luminescence properties of octahedral YVO4:Eu microcrystals

Uniform octahedral YVO₄:Eu³⁺ microcrystals have been successfully prepared through a designed two-step hydrothermal conversion method. One-dimensional precursor Y₄O(OH)₉NO₃ was first prepared through a simple hydrothermal process without using any surfactant, catalyst or template. Subsequently, well-defined octahedral YVO₄ was synthesized at the expense of the precursor during a hydrothermal conversion process. XRD results demonstrate that the diffraction peaks of the final product can be well indexed to the pure tetragonal phase of YVO₄. The SEM and TEM images indicate that the as-prepared YVO₄ sample has regular octahedral shape with sharp corners and well-defined edges. The as-obtained YVO₄:Eu³⁺ phosphor shows strong red emission under ultraviolet excitation or low-voltage electron beam excitation. Furthermore, this facile and general conversion method may be of much significance in the synthesis of many other lanthanide compounds with uniform morphology.     

Preparation of Sb2S3 nanomaterials with different morphologies via a refluxing approach

Single-crystalline antimony trisulfide (Sb₂S₃) nanomaterials with flower-like and rod-like morphologies were successfully synthesized under refluxing conditions by the reaction of antimony trichloride (SbCl₃) and thiourea with PEG400 and OP-10 as the surfactants. X-ray diffraction (XRD) indicates that the obtained sample is orthorhombic-phase Sb₂S₃ with calculated lattice parameters a=1.124 nm, b=1.134 nm and c=0.382 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the flower-like Sb₂S₃ is 9–10 μm in size, which is composed of thin leaves with thickness of 0.05–0.2 μm, width of 0.8–2.2 μm and length of 2.5–3 μm, and the rod-like Sb₂S₃ is 45–360 nm in diameter and 0.7–4 μm in length, respectively. UV–Vis analysis indicates that the band gap of Sb₂S₃ nanorods is 1.52 eV, suitable for photovoltaic conversion. A possible mechanism of formation was proposed. The effects of reaction time and surfactants on the growth of nanomaterials with different morphologies were also investigated.     

A partial molar volume for La2O3 in silicate melts

The densities of several La-bearing silicate melts distributed along binary joins have been measured using the double-bob Archimedean method. The results show that the addition of La₂O₃ leads to an increase in the melt density. From these density data, the partial molar volume of La₂O₃ in silicate melts has been determined. Distinct values for partial molar volume of La₂O₃ have been obtained (i.e., 44.01 and 37.04 cm³/mol at 1273 K for the La₂O₃-Na₂O-SiO₂ and La₂O₃-CaO-MgO-Al₂O₃-SiO₂ systems, respectively) indicating a compositional dependence of the partial molar volume of La₂O₃. Nevertheless, a single value for the partial molar volume of La₂O₃ (i.e., 43.47 cm³/mol at 1273 K) suffices to describe the molar volume of melts within errors in the entire multi-component system La₂O₃-Na₂O-CaO-MgO-Al₂O₃-SiO₂ and for La₂O₃ concentrations not greater than 7 mol%. In addition, this work points out that the molar volumes behave ideally within the composition range investigated (i.e., linear variation of the molar volume along the binary joins). Distinct values for the partial molar volume of La₂O₃ obtained in this study and their differences with the molar volumes of molten La₂O₃ given in the literature raise the possibility however that this ideality is not maintained within the entire system.     

Growth and properties of layered oxycarbonate Bi2Sr4Cu2CO3O8 single crystals

Layered oxycarbonate Bi₂Sr₄Cu₂CO₃O₈ single crystals have been obtained for the first time by free growth in closed vapor-phase cavities. The morphology, structure, composition, and superconducting properties of these crystals have been investigated.     

Vitrification and crystallization in the system of K2O-B2O3-TiO2

The vitrification and crystallization behavior of melts produced at 1400 °C in the ternary system of K₂O-B₂O₃-TiO₂ is investigated. It is shown that there are two fields of compositions (indicated in mol%) which allow obtaining the glass-ceramic materials with continuous glassy matrix after the cooling of molten compositions. In the first field [TiO₂] = 25-57, [K₂O] = 30-50 and [B₂O₃] = 0-25, the glass-ceramics consisted of the potassium-titanium-borate glassy phase and different crystalline potassium titanates (K₄Ti₃O₈, K₂Ti₂O₅, K₂Ti₄O₉, K₂Ti₆O₁₃). The ratio of TiO₂:K₂O in the obtained titanates increases with [TiO₂] and [B₂O₃]. In the second field, [TiO₂] = 7-37, [K₂O] = 0-25 and [B₂O₃] = 52-93, the obtained glass-ceramics consisted of a similar vitreous phase, as mentioned above, and TiO₂ crystals. During the cooling of the melts, short whiskers-like crystals of anatase formed in the compositions with relatively low [TiO₂] and relatively high [K₂O], whereas long fiber-shaped crystals of rutile appeared with the compositions characterized with relatively high [TiO₂] and relatively low [K₂O]. The possible application of the obtained glass-ceramic materials as a source of fibrous TiO₂, for composite reinforcement, and as solid lubricants is discussed.     

Growth and scintillation properties of the Na2W2O7 crystal

The growth and scintillation properties of the Na₂W₂O₇ crystal are reported. The solid reaction between Na₂CO₃ and WO₃ is used to synthesise the Na₂W₂O₇ material. The Na₂W₂O₇ single crystal has been grown by the Bridgman method. And the Na₂W₂O₇ single crystal with sizes 14×7×6 mm³ has been achieved. The transmission spectra, the Ultraviolet fluorescence spectra and the X-ray excited luminescence spectra of the Na₂W₂O₇ crystal are measured. The measurement results show that the Na₂W₂O₇ crystal is a promising intrinsic scintillator.