A. K. Sahu; Priyambada Mallick; S. K. Satpathy; Banarji Behera
Abstract
Synthesis of polycrystalline samples of Bi1-xNdxFeO3 [x = 0.5, 0.6, 0.7 and 0.8] were demonstrated following solid-state reaction method at high temperature. The structural properties of the sample were confirmed through the X-ray diffraction technique. The dielectric study of the compounds was performed ...
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Synthesis of polycrystalline samples of Bi1-xNdxFeO3 [x = 0.5, 0.6, 0.7 and 0.8] were demonstrated following solid-state reaction method at high temperature. The structural properties of the sample were confirmed through the X-ray diffraction technique. The dielectric study of the compounds was performed at different frequencies in the range of 100 Hz – 10 6 Hz for various temperatures. The non-Debye type of relaxation process confirmed from impedance analysis. The materials showed a negative temperature coefficient of resistance (NTCR) behavior at various temperatures and frequencies. AC conductivity of the materials with frequency at different temperatures satisfied the universal power law of Johnscher. Thermistor constant (β), sensitivity factor (α), and stability factor for all the samples were calculated and confirmed the characteristics of NTC thermistor.
Jie Cai; Xiaozhou Zhou; Yuanqiang Tu; Guanwen Feng; Chunyan Huang
Abstract
A sensitive electrochemical sensor for detection of sudan was developed based on solid-phase extraction (SPE) at bismuth-film modified glassy carbon electrode. SPE of sudan may be due to the physical adsorption between sudan and the bismuth film. The properties of the bismuth-film electrode (BiFE) designed ...
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A sensitive electrochemical sensor for detection of sudan was developed based on solid-phase extraction (SPE) at bismuth-film modified glassy carbon electrode. SPE of sudan may be due to the physical adsorption between sudan and the bismuth film. The properties of the bismuth-film electrode (BiFE) designed for detection Sudan were examined by scanning electron microscopy (SEM), electrochemical impedance and voltammetry. The various bismuth plating solutions containing Cl-, Br- and I- respectively, were tested in bismuth-film generation. It has been found that the plating solution only containing Br- ensures the finest quality bismuth film for analytical purposes. Other operational parameters such as extraction time, pH of the electrolytic and sample solution, and co-solvents have been optimized. Under the optimum experimental conditions, the stripping voltammetric response was proportional to the concentration of sudan ranging from 0.1 to 10 M. The detection limit was 0.05 M.
Subrat K. Barik; R.N.P. Choudhary; A.K. Singh
Abstract
The AC impedance and conductivity properties of Ba0.8Sr0.2TiO3 ceramics in a wide frequency range at different temperatures have been studied. The compound was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis of the compound by X-ray diffraction technique ...
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The AC impedance and conductivity properties of Ba0.8Sr0.2TiO3 ceramics in a wide frequency range at different temperatures have been studied. The compound was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis of the compound by X-ray diffraction technique confirmed its single phase. An ac impedance spectroscopic technique was used to correlate between the microstructure and electrical properties of the compound. The presence of both grain (bulk) and grain boundary effect in the compound was observed. The frequency-dependent electrical data were used to study the conductivity mechanism. An analysis of the electric impedance and modulus with frequency at different temperatures has provided some information to support suggested conduction mechanism.
N.S. Dhoble; V.B. Pawade; S.J. Dhoble
Abstract
Eu 2+ luminescence in novel Sr3.5Mg0.5Si3O8Cl4 and Ba3.5Mg0.5Si3O8Cl4 phosphors is reported in this paper. These were synthesized by combustion method at 550 o C furnace temperature. The prepared phosphors shows PL emission spectra at 445 nm, due to 4f 6 5d 1 → 4f 7 transition of Eu 2+ ions by monitoring ...
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Eu 2+ luminescence in novel Sr3.5Mg0.5Si3O8Cl4 and Ba3.5Mg0.5Si3O8Cl4 phosphors is reported in this paper. These were synthesized by combustion method at 550 o C furnace temperature. The prepared phosphors shows PL emission spectra at 445 nm, due to 4f 6 5d 1 → 4f 7 transition of Eu 2+ ions by monitoring excitation at 358 nm for Sr and Ba host lattice. Phase purity was checked by using XRD-pattern. The prepared phosphors have potential applications for solid-state lighting purpose.
Roshani Singh; S.J. Dhoble
Abstract
Eu 3+ and Dy 3+ doped strontium vanadium oxide (Sr2V2O7) phosphor has been successfully synthesized using solid state diffusion method and characterized by XRD as well as photoluminescence (PL) measurements. The PL emission of Eu 3+ ion was observed in Sr2V2O7 phosphor at 593 nm and 618 nm in orange ...
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Eu 3+ and Dy 3+ doped strontium vanadium oxide (Sr2V2O7) phosphor has been successfully synthesized using solid state diffusion method and characterized by XRD as well as photoluminescence (PL) measurements. The PL emission of Eu 3+ ion was observed in Sr2V2O7 phosphor at 593 nm and 618 nm in orange and red region of the spectrum, which corresponds to 5 D0→ 7 F1, 5 D0→ 7 F2 transitions, at the excitation wavelength of 393 nm. The PL emission of Dy 3+ ion was observed in Sr2V2O7 phosphor at 484 nm and 575 nm in blue and yellow region of the spectrum, which corresponds to 4 F9/2→ 6 H15/2 and 4 F9/2 → 6 H13/2 transitions, at the excitation wavelength of 349 nm. The 300 – 400 nm is Hg free excitation, which is characteristic of solid state lighting. Hence, Sr2V2O7 :RE [RE = Eu 3+ and Dy 3+ ] phosphors may be efficient materials for solid state lighting.
Huibin Xu; Hui Yang; Quanxiang Luo; Youliang Zeng; Bofang Zhou; Changhua Du
Abstract
The semi-solid stirring brazing process of SiCp < /sub>/A356 composites and 2024 aluminum alloy was investigated. The two substrates were heated up to the semisolid temperature range of Zn27Al filler metal in the joint region by a resistance heating plate in air. At this point a stirrer was penetrated ...
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The semi-solid stirring brazing process of SiCp < /sub>/A356 composites and 2024 aluminum alloy was investigated. The two substrates were heated up to the semisolid temperature range of Zn27Al filler metal in the joint region by a resistance heating plate in air. At this point a stirrer was penetrated into the semi-solid weld seam in order to mix filler metal and the two sides of substrates into a single uniform joint. After stirring, specimens were sectioned for analysis of macro- and micro-structures along the weld region. The research shows that SiCp < /sub>/A356 composites and aluminum alloy can be successfully joined with semi-solid filler metal by optimizing stirring temperature. It can be found that most of the oxide film on the surface of the base metal was disrupted and removed through the observation by SEM. The metallurgical bonds formed between the filler metal and the base materials. Since the semisolid temperature range of filler metal is narrow, the accurate controlling of weld pool temperature must be considered.
Pragna Kiria; Geoff Hyett; Russell Binions
Abstract
Solid-state thermochromic materials undergo semiconductor to metal transitions at a ‘critical temperature’, Tc. This review begins by describing the phenomenon of thermochromism, whereby the optical properties of a material change reversibly as a result of a change in temperature. The various ...
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Solid-state thermochromic materials undergo semiconductor to metal transitions at a ‘critical temperature’, Tc. This review begins by describing the phenomenon of thermochromism, whereby the optical properties of a material change reversibly as a result of a change in temperature. The various different types of thermochromism will be introduced with a focus on the thermochromism exhibited by solid-state materials. The fundamental chemical principles that describe the electronic structure and properties of solids, and the chronological developments in the theory behind the thermochromic transitions (such as, the effects of electron-electron interactions and structural phase changes due to lattice distortions) that led to the discovery of the semiconductor-to-metal transition, are presented. An extensive discussion of vanadium and titanium oxides is presented with a particular focus on vanadium (IV) oxide since its transition temperature is closest to room temperature. Observations and current understanding of the nature of the semiconductor-to-metal transition exhibited by these materials is detailed. The possibility of fine-tuning the transition temperature by introducing various dopants into the vanadium (IV) oxide lattice is examined and the effects of dopant charge and size is examined. Solid-state thermochromic materials may be exploited in areas such as microelectronics, data storage, or intelligent architectural glazing, thus are required to be synthesised as thin films for use in such applications. The numerous synthetic techniques (PVD, sol-gel method, PLD, CVD, APCVD and AACVD), for making metal oxide thermochromic thin films are described in reference to the production of vanadium (IV) oxide and compared. Finally rare earth nickelates exhibiting thermochromism are described.
