PDF Card Research Articles

Dysprosium doped SrCeO3 nanophosphors for advanced photochemical applications: Synthesis, characterization, photo-assisted dye degradation and latent fingerprint visualization

The present work investigates the novel potential of Sr(1-x)CeO3: xDy3+ (x = 1–9 mol%) nanoparticles, fabricated through Solution Combustion method using citric acid as fuel. The as-fabricated samples were thoroughly characterised using a variety of techniques to obtain structural, morphological, and optical data. Powder X-ray diffraction (PXRD) examination revealed the presence of an orthorhombic crystal structure (Pnma) matching PDF card #01-083-1156. Tauc's plot evaluating band gap energy utilizing absorption spectra reveals a range of 3.4 eV–4.2 eV with refractive index ranging from 0.64 to 1.22. Using Field Emission Scanning Electron Microscopy (FESEM), it was possible to see a coral-like aggregation for the host and initial concentration of Dy3+ ions, and a porous structure for higher concentrations. With an average particle size of 38.20 nm, a comprehensive Transmission Electron Microscopy (TEM) study demonstrates the fused aggregation structure. Moreover, quantifiable evidence of the precursors presence is provided by X-ray Photoelectron Spectroscopy (XPS). For the as-fabricated samples, photoluminescence investigations were carried out. Two strong peaks with a dominating 4F9/2 → 6H13/2 diploe-dipole transition was seen in the observed emission spectra under 366 nm (6H15/2 → 6P7/2) excitation. These peaks are positioned at 573 nm (4F9/2 → 6H13/2) and 478 nm (4F9/2 → 6H15/2). Under UV light, two cationic dyes, Rhodamine-B (Rh–B) and Methylene Blue (MB), were photo-catalytically degraded using the prepared sample (SCD5). According to 0th and 1st order kinetics, the observed data show evidence of effective degradation up to 89.64 % (Rh–B) and 78.86 % (MB) at 80th minute. In addition, the impact of several analytical parameters on the percentage degradation of Rh–B and MB dyes was investigated. These parameters included catalyst changes, dye dosage, and scavenger effect. The produced nanoparticles were used to create latent fingerprints on two non-porous surfaces: glass and aluminium. The results clearly showed that on both surfaces a type-III level of detection was attained. To summarise, the outcomes indicate that Sr(1-x)CeO3: xDy3+ nanoparticles that have been synthesized can be used for advanced forensic applications as well as for the degradation of dye pollutants.

Characteristics of Natural Ti-Bearing Nanoparticles in Groundwater within Karst Areas of Northern China

Karst areas are widespread in China and can be divided into southern karst and northern karst based on the geographical boundary of Qinling Mountains and Huaihe River. In northern karst regions, karst springs are the predominant landform. Previous studies on karst springs have predominantly focused on macroscopic perspectives, such as water chemistry characteristics, with less attention given to the microscopic characteristics of springs. Therefore, this study focused on the Jinan Baotu Spring area, representative of a typical northern karst region, and investigated the natural nanoparticles present in different aquifers at various depths from a microscopic point of view. Through the observation of nanoparticle tracking analyzer (NTA), numerous nanoparticles were identified in the groundwater samples. The particle size range of the particles contained in groundwater is mainly concentrated in the range of 150–500 nm, and the particle concentration is mainly concentrated in the range of 1.5–5.0 × 105 Particles/L. The microstructure, chemical composition, and element distribution of these nanoparticles were analyzed using TEM-EDS techniques. The results unveiled the presence of Ti-bearing nanoparticles in various groundwater layers, including both crystalline and amorphous states, as well as nanoparticles exhibiting the coexistence of crystal and amorphous structures. By comparing the measured lattice spacing with PDF cards, the crystalline Ti-bearing nanoparticles were identified as rutile, brookite, anatase, ilmenite, pseudorutile, and ulvospinel. Furthermore, the main components of the amorphous Ti-bearing nanoparticles predominantly consisted of Ti or a mixture of Ti and Fe. EDS analysis further indicated that the Ti-bearing nanoparticles carried additional metal elements, such as Zn, Ca, Mn, Mo, Cr, and Ni, suggesting their potential role as carriers of metal elements during groundwater transportation. This discovery provided new insights into the migration of metal elements in groundwater and underscores the capacity of nanoparticles to enhance the mobility of inorganic substances within the water environment. Notably, brookite was detected in three different areas, including the direct discharge area, indirect recharge area, and discharge area, which may indicate that some special natural nanoparticles could serve as natural mineral tracer particles in the process of groundwater migration.

Deciphering the Roles of Chemistry and Structure in Iridium Oxide Oxygen Evolution Catalysts through the Study of Annealed Iridium Oxide Nanoparticles

The development of proton exchange membrane (PEM) water electrolysis, which enables the production of de-carbonized hydrogen, is hindered by the low efficiency of the oxygen evolution reaction (OER). This is especially true in acidic environment where only noble metals (mainly Ru and Ir) can be used as electrocatalysts. Iridium oxide nanocatalysts (IrOx) are promising due to their high OER activity and good resistance to acidic and oxidative conditions. However, finding a compromise between their electrocatalytic activity and stability remains challenging. Moreover, it is not yet clear which parameter (the material structure1 or the initial iridium oxidation state2) controls these two properties.To address these challenges, we synthesized IrOx nanoparticles (NPs) supported on carbon (IrOx/C), through a modified polyol process, and annealed them under air, at temperatures ranging from 200◦C to 850◦C. This allows us to deconvolute the effects of the oxidation state, the structure and the size of IrOx NPs and to tune their activity and stability3. To analyze the structure, morphology, and oxidation state of Ir in these catalysts, we used transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and both laboratory-based and synchrotron-based X-ray diffraction (XRD) techniques.We observed in situ the crystallization of IrOx NPs, leading to crystallite size growth and change in Ir electronic state (see Figure 1a). Additionally, we investigated the morphological changes of IrOx NPs with respect to annealing temperature (refer to Figure 1b-f). We assessed their electrocatalytic activity towards the OER and determined their stability number4 (S-number) using inductively coupled plasma mass spectrometry and electrochemistry. We observed that increasing the annealing temperature led to an increase in particle size and degree of crystallinity, but did not result in significant changes in the iridium oxidation state (refer to Figure 1g). We observed the evolution of the electrochemical activity of the nanoparticles with the annealing temperature (see Figure 1h). Our results show a correlation between the changes in electronic structure, morphology, and size, and the evolution of OER activity and stability of the IrOx NPs. Specifically, we identified certain conditions that achieved an optimal balance between activity and stability.(1) Elmaalouf, M.; Odziomek, M.; Duran, S.; Gayrard, M.; Bahri, M.; Tard, C.; Zitolo, A.; Lassalle-Kaiser, B.; Piquemal, J.-Y.; Ersen, O.; Boissière, C.; Sanchez, C.; Giraud, M.; Faustini, M.; Peron, J. Nat. Commun. 2021, 12 (1), 3935. https://doi.org/10.1038/s41467-021-24181-x.(2) Claudel, F.; Dubau, L.; Berthomé, G.; Sola-Hernandez, L.; Beauger, C.; Piccolo, L.; Maillard, F. ACS Catal. 2019, 9 (5), 4688–4698. https://doi.org/10.1021/acscatal.9b00280.(3) Geiger, S.; Kasian, O.; Shrestha, B. R.; Mingers, A. M.; Mayrhofer, K. J. J.; Cherevko, S. J. Electrochem. Soc. 2016, 163 (11), F3132. https://doi.org/10.1149/2.0181611jes.(4) Geiger, S.; Kasian, O.; Ledendecker, M.; Pizzutilo, E.; Mingers, A. M.; Fu, W. T.; Diaz-Morales, O.; Li, Z.; Oellers, T.; Fruchter, L.; Ludwig, A.; Mayrhofer, K. J. J.; Koper, M. T. M.; Cherevko, S. Nat. Catal. 2018, 1 (7), 508–515. https://doi.org/10.1038/s41929-018-0085-6.Acknowledgments: This work was supported by the French National Research Agency in the frame of the MATHYLDE project (grant number n° ANR-22-PEHY-0001).Figure 1 – a. X-ray diffractograms obtained on IrOx/C annealed at 290, 340, 380, 420, 470, 520, 570, 620, 670 and 850°C under air. Each measurement lasted 13 minutes. The hashes correspond to tetragonal IrO2 (PDF card 00-043-1019) and the stars to metallic Ir (PDF card 00-006-0598). b-f. TEM images of IrOx/C NPs as-synthesized and calcined at 290, 380, 420, 570 and 850 °C. g. X-ray photoelectron spectra showing the Ir 4f levels of IrOx/C NPs as-synthesized and calcined at 380, 420, 520 and 850 °C. The dotted lines indicates the theoretical position of the peaks for Ir(IV) and Ir(III). h. Cyclic voltammograms measured in 0.1 M HClO4 at 50 mV s−1 indicating the change in electrochemical properties of IrOx/C NPs with annealing temperature. Figure 1

(Digital Presentation) Fabrication and Characterization of 4Sc4YSZ/LSM-4Sc4YSZ Novel Electrode-Supported Half-Cell Composition for Solid Oxide Electrochemical Cells

Scandium and Yttrium co-doped ZrO2 (4Sc4YSZ) thin film solid electrolyte has exhibited improved conductivities and phase stability by considering advantages of both Y-doped zirconia (YSZ) and Sc-doped zirconia (ScSZ). To further investigate the promising properties of this co-doped composition, a solid electrolyte thin film of 4Sc4YSZ deposited on a new LSM-4Sc4YSZ composite electrode was conducted. In this study, the effect of pre-sintering temperature (1000°C, 1150°C, and 1300°C) of the LSM-4Sc4YSZ electrode substrate in the deposition of a dense solid electrolyte film was studied. X-ray diffraction (XRD) analysis of all the LSM-4Sc4YSZ composite electrodes revealed distinct phases of rhombohedral LSM and cubic 4Sc4YSZ. Also, the thin film electrolytes exhibited cubic 4Sc4YSZ with calculated lattice parameters of a equal to 5.10 Å, 5.10 Å, and 5.09 Å deposited on the electrode substrate pre-sintered at 1000°C, 1150°C, and 1300°C, respectively. The obtained lattice parameters were comparable with the reference LSM (PDF card no. 000-053-0058) and 4Sc4YSZ (PDF card no. 01-080-4524). Morphological characterization via scanning electron microscopy (SEM) showed that the thin film solid electrolyte with LSM-4Sc4YSZ electrode pre-sintered at 1300°C has a relatively dense microstructure than those with lower pre-sintering electrode temperatures. In addition, the thin film deposited on the 1300°C LSM-4Sc4YSZ obtained the lowest average thickness of 12.81 µm as compared to the 1000°C and 1150°C LSM-4Sc4YSZ with thickness values of 38.32 µm and 27.99 µm, respectively. The electrochemical performance of the fabricated half-cell was analyzed using electrochemical impedance spectroscopy (EIS). The total conductivity, as calculated from the EIS results, of 4Sc4YSZ/LSM-4Sc4YSZ half-cell pre-sintered at 1300°C is 0.0726 S/cm at 700°C under oxygen gas flow environment.

Combustion synthesized novel SrAlBO4:Eu3+ phosphor: Structural, luminescence, and Judd-Ofelt analysis

A series of new phosphor SrAlBO4 doped by Eu³+ was synthesized by using very known Combustion method. The structural and optical properties explored using X-ray diffraction (XRD). The XRD pattern was matched well with the standard PDF card no. 1542236.The obtained phosphor had orthorhombic structure with space group Pccn (56). The image of Scanning electron microscope shows the external morphology of SrAlBO4 phosphor material, which revails the irregular morphology and the material showed the non uniform structure with agglomerates' size was size ranging in several micrometers. The confirmation of present element and their percentage also shown in the EDX image. The luminescence properties of rare earth activated SrAlBO4 phosphor were determined by measurement of excitation and emission spectra. The PL emission spectra of Eu3+ doped SrAlBO4 phosphor show characteristics bands at 590 nm & 614 nm which corresponds due to 5D0 →7F1 and 5D0 →7F2 transition of Eu3+ ions upon 395 nm excitation. The effect of different concentration of Eu3+ on luminescence emission intensity of SrAlBO4 phosphor was also studied. Further, concentration quenching is explained using Blasse's equation and Dexter's theory. Also, Judd-Ofelt analysis was performed on photoluminescence emission spectra. On investigation synthesized rare earth activated SrAlBO4 phosphor can be suitable for all lighting application devices.

Synthesis and effects of co-dopants (La3+ , Sm3+ , Mn2+ , Nd3+ , V5+ , Y3+ ) on photoluminescence of SrAl2 O4 :Dy3+ phosphor.

In this research, the co-dopant effects on photoluminescence (PL) properties of SrAl2 O4 :Dy3+ phosphors were studied. The phosphor powders were prepared with solid state reaction, which is the method that is frequently preferred in SrAl2 O4 phosphors and efficient results are obtained in terms of PL properties. X-ray diffraction (XRD) patterns of all co-doped samples were fitted with pdf card#01-034-0379. Fourier-transform infrared (FTIR) analysis supports the phase evolution determined in the XRD results. PL examinations started with the SrAl2 O4 that was synthesized with the addition of boron, and then continued with the doped/and co-doped samples. Except for the Sm3+ co-doped phosphor, PL data of characteristic Dy3+ transitions were obtained for other lanthanide and metal ion co-dopants. The strongest PL intensity was demonstrated in the SrAl2 O4 :Dy3+ ,V5+ . SrAl2 O4 :Dy3+ ,Sm3+ phosphor shows both the Dy3+ and Sm3+ ions transition related peaks appeared in the same spectrum. In the continuation of the studies, SrAl2 O4 :Dy3+ ,Sm3+ and SrAl2 O4 :Dy3+ ,V5+ powders were immersed in water for 2 h. Regardless of the presence of Dy3+ luminescent centers and other co-dopants, broadband and intense blue emission peak at 445 nm was recorded which is directly related to newly formed phases by the decomposition of SrAl2 O4 .

Weak anti-localization properties of high-quality topological Bi2Te3 nanofilms prepared by home-built pulsed laser enhanced molecular epitaxy system

Efficient preparation of high-quality topological insulator nanofilms (TINFs) in large scale is demanding. Using a home-built pulsed laser enhanced molecular epitaxy system (PLEES), we efficiently fabricate TINFs with prefect stoichiometry using Bi2Te3 TINFs as an example. Instead of utilizing multiple beam source furnaces to provide essential elements, hybrid targets containing both pure Bi2Te3 and Te targets are applied in a single epitaxial chamber. Moreover, diffraction pattern of growing Bi2Te3 TINFs are monitored in live by a high-energy electron diffractometer, allowing fast optimization of growth conditions. Scanning electron microscopy and atomic force microscopy demonstrate that the surface morphology of the prepared Bi2Te3 nanofilms with a thickness of 70 nm are flat and dense, and energy-dispersive X-ray spectroscopy analysis suggests that the ratio of Bi to Te elements is 2:3. The grazing incidence X-ray diffractometer reveals that the X-ray diffraction peaks of the synthesized nanofilm matches those of the Bi2Te3 standard PDF card. The prepared nanofilm exhibits a weak anti-localization effect at low magnetic fields characterized by physical property measurement system, confirming its unique electrical transporting properties. This work demonstrates that using hybrid targets with optimized growth parameters enable PLEES to efficiently grow high-quality stoichiometric TINFs on a large scale.

A type of X-ray diffractometer with adaptive X-ray spot sizes

In order to realize micron scale to millimeter scale phase structure analysis, as well as accurate phase structure analysis of surface uneven samples, X-ray diffractometer named Hawk-II, which can adaptively adjust the diameter of irradiated X-ray beam spot according to the diameter of internal tangential circle at the measured point, is developed by combining X-ray diffraction technology, CCD camera imaging technology and slightly-focusing ploycapillary X-ray control technology. The X-ray source system, six-dimensional linkage motion system, CCD camera, detection system and control system based on LabVIEW are the main components of the Hawk-II. Compared with the 3°–5° divergence of the conventional X-ray source, the divergence of the X-ray emitted by the slightly-focusing polycapillary X-ray optics is only about 0.15° and also the intensity within the beam spot range is dozens of times stronger. Therefore, the shift of peak position will not appear due to the pores, curvature or uneven surface of the sample, when Hawk-II is used to analyze the samples with irregular surface. The diffraction pattern of the uneven Ren Min Bi five-cent coin are collected in the Hawk-II and PANalytical X-Pert Pro MPD conventional X-ray diffractometer respectively. By comparing the analysis results, it is found that the diffraction peaks measured by the X-Pert Pro MPD are shifted seriously, with a maximum deviation angle of 0.52°. While the diffraction peaks detected by the Hawk-II are basically consistent with the data from the standard PDF card, which verifies the advantages of the analysis of irregular samples by the Hawk-II. In order to explore the difference between different beam spots used for analysis at the same point, red and green porcelain fired in Qing dynasty and GaAs-based Cu and Fe plated films are analyzed by the Hawk-II. It is found that when the samples are relatively uniform, the intensities of diffraction peaks of different beam spots are relatively close, while when the samples are not uniform, the diffraction peaks vary greatly. Especially, some microcrystalline phases can be detected only with large beam spots. In addition, to verify the adaptive functionality of the Hawk-II, a bronze from the Western Han Dynasty, with different rust spots on it, is tested. It is found that the Hawk-II can adjust the beam spot size according to the different corrosion points, making the irradiation area coincide with the area to be analysed and the phase structure detected more accurately. Therefore, the Hawk-II is a general purpose X-ray diffractometer, which has the analytical capability from micron scale to millimeter scale and the energy dispersive X-ray fluorescence analysis function. Moreover, it has the advantages of the accurate analysis of irregular samples, fast detection speed, simple operation, etc. Based on the above analysis, the Hawk-II will be widely used in different fields.

Microwave dielectric properties and sintering behaviors of Zn1.8SiO3.8 ceramics

Zn2SiO4 ceramics are important candidates for microwave dielectric materials applied in wireless communication. However, the appearance of the second phase and stomatal impurity affect the microwave dielectric properties. In this work, Zn2SiO4 ceramics were prepared by the conventional solid-state process under different temperatures according to Zn-deficient formula to suppress the formation of secondary phase. X-ray diffraction showed peaks that coincide with those of Zn2SiO4 PDF card standard without secondary phase. Scanning electron microscopy revealed that there were uniform crystal grains at 1300 °C, and larger grains sizes yielded smaller pore gaps. The dielectric properties of Zn1.8SiO3.8 ceramics sintered at 1300 °C were estimated to er = 6.451, Q*f = 102,807 GHz, and τf = -32 ppm/°C.. In summary, Zn1.8SiO3.8 ceramics had potential applications in wireless communication technology due to their excellent dielectric property.

Influence of annealing conditions on tripe-layer TiO2/Si3N4/SiO2 antireflection coatings for GaAs solar cells

In this work, TiO2/SiO2/Si3N4 triple-layer antireflection coatings (TLARC) were prepared on GaAs substrate by RF sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD). Influence of annealing conditions on the structure and optical properties of TLARC were also investigated. The structure and optical proprieties were analyzed by Grazing Incidence Angle X-ray Diffraction (GIXRD) Fourier Transform Infrared Spectroscopy (FT-IR), Atomic Force Microscopy and UV-VIS spectroscopy. The experimental results were summarized as follows: diffraction peaks of SiO2, Si3N4 and TiO2 respectively appeared in the as-deposited status, and after annealing, new diffraction peak at 25.2° corresponds to TiO2 was confirmed by checking out PDF cards; Stretching vibration of Ti=O, Si-O-Si and N-Si-N was confirmed by FT-IR spectrum; The average reflectance of the TLARC after annealing at 750 °C and holding for 5 min reached the lowest value, which was approximately 7.84 %.

Investigation on Inclusions in Non-oriented Silicon Steels

Inclusions in non-oriented electrical steels were automatically measured using Explorer 4 and extracted with a non-aqueous solution electrolytic method to observe their three-dimension morphology. Extracted inclusions were collected and prepared for micro-XRD test, which is performed to identify the crystal structure of inclusions. Inclusions mainly consist of AlN with P63mc structure, MnS with Fm-3m structure and Al2O3 with R-3c structure, and calculated lattice parameters of inclusions almost agree with that listed in standard PDF cards.

Cathodoluminescence and thermoluminescence of ZnB2O4:Eu3+ phosphors prepared via wet-chemical synthesis

In present work, a series of Eu doped zinc borate, ZnB2O4, phosphors prepared via wet chemical synthesis and their structural, surface morphology, cathodoluminescence (CL) and thermoluminescence (TL) properties have been studied. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements (XRD) and they were well consistent with PDF card No. 39-1126, indicating the formation of pure phase. The thermoluminescence (TL) behaviors of Eu activated ZnB2O4 host lattice are studied for various beta doses ranging from 0.1 to 10 Gy. The high-temperature peak of Eu activated sample located at 192 °C exhibited a linear dose response in the range of 0.1–10 Gy. Initial rise (IR) and peak shape (PS) methods were used to determine the activation energies of the trapping centres. The effects of the variable heating rate on TL behaviour of Eu activated ZnB2O4 were also studied. When excited using an electron beam induced light emission (i.e cathodoluminescence, CL) at room temperature (RT), the as-prepared phosphors generate reddish-orange color due to predominant emission peaks of Eu3+ ions located at 576–710 nm assigned to the 5D0→7FJ (J=1,2,3, and 4) transitions. The maximum CL intensity for Eu3+ ions at 614 nm with transition 5D0→7F2 was reached Eu3+ concentration of 5 mol%; quenching occurred at higher concentrations. Strong emission peak for Eu3+ ions at 614 nm with transition 5D0→7F2 is observed. The CL experimental data indicate that ZnB2O4:Eu3+ phosphor as an orange-red emitting phosphor may be promising luminescence materials for the optoelectronic applications.

Seebeck coefficient of Cu2ZnSnS4 film synthesized by sol-gel process

This work, we reported on the effect of annealed to characterized and Seebeck coefficient of Copper-Zinc-Tin-Sulfide (Cu2ZnSnS4; CZTS). The CZTS film was deposited on glass slide by dip-coating technique. The precursor solution was prepared by dissolved Copper chloride, Zinc chloride, Tin chloride, and Thiourea in 2-methoxyethanol and drop mono-ethanolamine as stabilizer. The CZTS was dried at 473 K and annealed at 573 K, and 673 K. The formation of crystal structures showed kesterite tetragonal structure in (112), (220), (312), (200), and (322) plans, and corresponding to PDF card number 00-026-0575. It was found that, the crystallite size and thickness are decreased, while lattice strain and Seebeck coefficients were increased with increasing annealed temperature, respectively. The Seebeck coefficient can optimized by observation temperature range of 573 and 673 K.

Preparation of Highly Crystallized Yttrium Oxysulfide Suspension via a Novel Colloidal Processing.

High-crystallized Y2O2S suspension was synthesized by a novel two-step method of high temperature solid-state reaction and subsequent colloidal processing. The synthesis method proposed in this study retains all advantages of the high temperature solid-state reaction method. The obtained data agrees with that of the PDF card, which indicates the product is pure Y2O2S crystals. The results show that the prepared Y2O2S particles are highly crystallized without any significant defects. The fine smooth particles were almost regular, exhibiting an approximately subspherical shape. Quantitative image analysis of particles suggests a mean particle size of 120±34 nm. That is to say, the yttrium oxysulfide colloid prepared by this method have a very narrow size distribution. The obtained ethanol suspension shows Tyndall effect when irradiated with laser of wavelength 532 nm. In addition, the particles exhibit excellent dispersibility in ethanol solution. This is rarely observed for the covalent compounds, which generally present poor dispersibility in solution. As is known to all, the state of the dispersion depends on the acid leaching process. The acid leaching process facilitates the adsorption of ethanol molecules on the surface of the particles. The electrostatic repulsive force among colloidal particles will improve their rheological properties and dispersibility in solution. In this study, the particles can be dispersed well in ethanol after acid leaching. The method'proposed in this study can be extended for the preparation of mono-dispersed oxysulfide nanophosphors and may provide an efficient way for the preparation of stable covalent compound dispersions.

New Method of Distinguishing X-Ray Diffraction Curves about Laser Structure

Come up with a new method of rocking curves analysis, its using the software of the double-crystal X-ray diffraction rocking curves analysis to simulate vertical cavity surface emitting laser structure. Simulate the X-ray diffraction rocking curve of each part of laser structure, and then compare with the diffraction rocking curve of the overall structure in order to acquire the adscription of each diffraction peak, the method can also be applied to other semiconductor lasers. Compared with conventional PDF card library about diffraction position of all material peaks, the method has the advantages of fast and accurately to distinguish, high efficiency. In the end, the X-ray diffraction rocking curves analysis method is applied to the MOCVD growth of GaAs based vertical cavity surface emitting laser, and quoting strain relaxation mechanisms for explaining the reasons for the partial peak drifting.

Preparation and study on performance of submicron nickel powder for multilayer chip positive temperature coefficient resistance

Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance (PTCR). The fine grain of ceramic powders and base metal nickel are necessary. This paper uses reducing hydrazine to gain submicron nickel powder whose diameter was 200–300 nm through adjusting the consumption of nucleating agent PVP properly. The submicron nickel powder could disperse well and was fit for co—fired of multilayer chip PTCR. It analyes the submicron nickel powder through x-ray Diffraction (XRD) and calculates the diameter of nickel by PDF cards. Using XRD analyses it obtains several conclusions: If the molar ratio of hydrazine hydrate and nickel sulfate is kept to be a constant, when enlarging the molar ratio of NaOH/Ni2+, the diameter of nickel powder would become smaller. When the temperature in the experiment raises to 70–80 °C, nickel powder becomes smaller too. And if the molar ratio of NaOH/Ni2+ is 4, when molar ratio of (C2H5O)2/Ni2+ increases, the diameter of nickel would reduce. Results from viewing the powders by optical microscope should be the fact that the electrode made by submicron nickel powder has a better formation and compactness. Furthermore, the sheet resistance testing shows that the electrode made by submicron nickel is smaller than that made by micron nickel.

Lattice deformation and phase transformation from nano-scale anatase to nano-scale rutile TiO 2 prepared by a sol-gel technique

Nano-scale rutile phase was transformed from nano-scale anatase upon heating, which was prepared by a sol-gel technique. The XRD data corresponding to the anatase and rutile phases were analyzed and the grain sizes of as-derived phases were calculated by Sherrer equation. The lattice parameters of the as-derived anatase and rutile unit cells were calculated and compared with those of standard lattice parameters on PDF cards. It was shown that the smaller the grain sizes, the larger the lattice deformation. The lattice parameter a has the negative deviation from the standard and the lattice parameter c has the positive deviation for both phases. The particles sizes had preferential influence on the longer parameter between the lattice parameters of a and c. With increasing temperatures, the lattice parameters of a and c in both phases approached to the equilibrium state. The larger lattice deformation facilitated the nucleation process, which lowered the transformation temperature. During the transformation from nano-scale anatase to rutile, besides the mechanism involving retention of the {112} pseudo-close-packed planes of oxygen in anatase as the {100} pseudo-close-packed planes in rutile, the new phase occurred by relaxation of lattice deformation and adjustment of the atomic sites in parent phase. The orientation relationships were suggested to be anatase {101}//rutile {101} and anatase <201>//rutile<111>, and the habit plane was anatase (101).

Characterizations of mixed Bi/V oxide films, deposited via sol–gel route, used as electrodes in asymmetric liquid crystal cells

In the search of new materials for electrodes in electrochromic devices and in asymmetric liquid crystal cells, some modified vanadium oxide thin films has been investigated. The new gels have been generated by the addition of 10% of bismuth (atomic ratio) to the precursors mixture. The sol–gel route started from metal alkoxides, vanadium oxo iso-propoxide and BiCl 3 dissolved in ethanol (99%), to give the atomic ratio Bi/V=1:10. The crystallization temperature of such bulk gels has been found by DTA analysis to occur at 320 °C, while only seeds of a crystal phase are found after annealing the dip-coated films at 400 °C, identified as Bi 4V 6O 21 (PDF card no. 33-222). Microscopic visual investigation and micro-Raman analysis were performed on the deposited films, “as grown” and “400 °C annealed”. Finally, the films have been tested as electrodes in asymmetric nematic liquid crystal (NLC) cells, to investigate the rectification effect. The electro-optic measurements were performed in modified nematic liquid crystal cells for both “as-deposited” and annealed films. The voltage dependence of the electro-optical response and the current flow have been analyzed at the same time in the voltage range −10/+10 V. A model based on the electrical interaction between both the indium tin oxide (ITO)-Bi/V oxide films and Bi/V oxide films–liquid crystal interfaces is proposed, to explain the electric and electro-optic asymmetric responses of the cells.

Improved crystallographic data for graphite

Powder diffraction pattern of SP-1 graphite has been obtained using synchrotron X-ray diffraction. Unit cell dimensions were calculated using a least-squares analysis that refined to a |Δ2θ°| of no more than 0.007. A hexagonal cell was determined with a space group of P63/mmc (194), a=2.4617(2) and c=6.7106 (4) Å. The Smith/Synder figure of merit is 167 based upon 11 peaks, which indicates that the quality of this data set is superior to the existing PDF card for graphite, 41-1487. It is also emphasized that the interlayer spacing of graphite should be 3.355(1) Å. Using GAS and EXPGUI codes, a new set of calculated powder diffraction data based upon the interlayer spacing of 3.555 Å is generated. A comparison with the current calculated card, 75-1621, has also been made.

Improved X-ray powder diffraction data for Ti2AlN

A complete set of d spacings, intensities, and h, k, l indexes for Ti2AlN has been determined from X-ray powder diffraction. The lattice parameters are a=2.989(2) Å, c=13.614(5) Å; in good agreement with previous work. The new set of results comprises seven reflections not present in the current Ti2AlN PDF card No. 18-70. Furthermore, a new set of relative intensities are reported that are in better agreement with the calculated values than they are with those listed in the PDF card.