High Temperature Solid State Research Articles

Second-Harmonic Generation and Crystal Structure of the Diamond-like Semiconductors Li2CdGeS4 and Li2CdSnS4

The semiconductors Li(2)CdGeS(4) and Li(2)CdSnS(4), which are of interest for their nonlinear optical properties, were synthesized using high-temperature solid-state and polychalcogenide flux syntheses. Both compounds were found to crystallize in Pmn2(1), with R1 (for all data) = 1.93% and 1.86% for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively. The structures of both compounds are diamond-like with the tetrahedra pointing in the same direction along the c axis. The alignment of the tetrahedra results in the structure lacking an inversion center, a prerequisite for second-harmonic generation (SHG). A modified Kurtz nonlinear optical powder technique was used to determine the SHG responses of both compounds. Li(2)CdGeS(4) displayed a type I phase-matchable response of approximately 70x alpha-quartz, while Li(2)CdSnS(4) displayed a type I non-phase-matchable response of approximately 100x alpha-quartz. Diffuse-reflectance spectroscopy was used to determine band gaps of 3.10 and 3.26 eV for Li(2)CdGeS(4) and Li(2)CdSnS(4), respectively.

Preparation of nanostructures NiO and their electrochemical capacitive behaviors

Nanocrystalline NiO was synthesized by high temperature solid-state (HTSS) method and microwave (MW) method. The structure of the samples was examined by X-ray. Electrochemical properties were examined by galvanostatic charge–discharge measurements, cyclic voltammetry and electrical impedance spectroscopy. The results showed that the particle sizes of the NiO prepared by MW and HTSS were 34.6 and 75.5 nm. The specific capacitance of MW and HTSS were 186 and 97 F g −1, which decreased to 170 and 74 F g −1 after 1000 cycles. It revealed that the NiO materials prepared by MW exhibited good specific capacitance and cycling performance, which had the high surface redox reactivity due to its special nanostructures.

Preparation of the ZnS-type Electroluminescent Phosphor Used in Flat Panel Display Field

ZnS electroluminescent phosphors were prepared by high temperature (1100℃) solid state reaction,subsequently milling for some time (t=0-180min) and the final low temperature annealing process (750℃).The as-synthesized phosphors were characterized by X-ray powder diffraction,UV-Vis diffuse reflectance spectra,scanning electron microscope and photoluminescence spectra.Electrolu- minescence performance was investigated on the screen-printing electroluminescent lamp at 100V and 400Hz.Increased milling time leads to intensity reductions and width increases of some diffraction peaks, and results in slight red-shifts of the absorption edges.Photoluminescence brightness declines about 58% after milling for 180 min while electroluminescence brightness increases from 14.39cd/m~2(t=0min) to the peak value 90.13cd/m~2(t=160min).The changes of photoluminescence and electroluminescence performances originate from the defects in the microstructure induced by milling.

Influence of Mechanical Milling and Annealing Atmosphere on the Photoluminescence Properties of ZnS:Cu,Cl Phosphors

ZnS:Cu,Cl phosphors were synthesized by high temperature (1200 °C) solid state reaction, mechanical milling (rotation speed = 0, 75, 150, 250 and 350 r / min) and the final annealing at 750 °C for 1 h in different atmospheres (hydrogen sulfide, sealed evacuated silica tubes and Ar). The as-prepared phosphors were characterized by X-ray powder diffraction and photoluminescence spectra. It was found that mechanical milling led to width increases of diffraction peaks. Both the mechanical milling and atmosphere play important roles in the photoluminescence performance of the phosphors. Some phosphors prepared by the three-step method possess higher photoluminescence performances than the normal one-step method. Particularly, the luminescence intensity of the phosphor milled at the rotation speed of 75 r / min and then treated in Ar atmosphere is about one time higher than that prepared by the normal one-step process.

Melting and high-temperature solid state transitions in cobalt(II) halides

Melting and high temperature solid-state transitions in CoCl2 and CoBr2 are widely discussed. On the basis of DSC and conductometric measurements it was found that melting process of CoCl2 is preceded by a solid-state transition appearing about 20 K below the melting point of CoCl2. Due to deconvolution of the thermograms, the enthalpy of fusion and that of solid-state transition were found to be 36.4 and 9.6 kJ mol–1, respectively. Melting points of CoCl2 and CoBr2 were established to be 999.0 and 949.7 K, respectively. Hitherto unknown enthalpy of fusion of CoBr2 was determined to be 27.2 kJ mol–1. A solid-state transition in CoBr2 at 650 K has been confirmed.

Sewage sludge as a single precursor for development of composite adsorbents/catalysts

New York City origin sewage sludge was pyrolyzed and converted into adsorbents. Pyrolysis conditions were modified in order to evaluate the development of catalytic surface towards hydrogen sulfide oxidation. The holding time ranged from 0.5 h to 2 h and the final temperature was 650 °C, 800 °C and 950 °C. The resulting materials were characterized using adsorption of nitrogen (surface area and pore volume), thermal analysis, X-ray diffractions, XRF, SEM-EDX, TEM and pH measurements. On these materials adsorption/oxidation of hydrogen sulfide from moist air was carried out and the products of the surface oxidation were evaluated. The results indicated development of catalytic surface with an increase in pyrolysis temperature and holding time. As a result of solid state high temperature reactions between main components of sewage sludge, mainly iron, zinc, copper, phosphorus, silica and alumina, new mineral phases are formed which are very active in the oxidation process. Moreover, the presence of catalytic metals and organic vapors results in formation of carbon nanotubes on the surface of sewage sludge derived adsorbents as a result of self imposed chemical vapor deposition process.

High-Temperature and Long-Term Stable Solid-State Electrolyte for Dye-Sensitized Solar Cells by Self-assembly

Ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was solidified by silica nanoparticles (> 2 wt %) even up to 85 degrees C. The mechanism of solid-state composites was inferred to self-assemble through hydrogen bond networks between the anion BF4- and the hydroxyl group in the surface of silica nanoparticles, which was characterized by differential scanning calorimetry measurement and Fourier transition infrared spectra. The solid-state composite was introduced to form high-temperature solid-state electrolytes for highly efficient dye-sensitized solar cells with an overall energy-conversion efficiency of 4.7% at room temperature and 5.0% at 60 degrees C under AM 1.5 sunlight illumination (75 mW cm(-2)).

Microwave-assisted solid-state synthesis of hydroxyapatite nanorods at room temperature

Hydroxyapatite (HAP) is the main inorganic constituent of human hard tissues, such as bones and teeth [1]. HAP is usually used in various physical forms such as granules, rods and coating over metallic implants. For example, Bone itself is a composite with HAP nanorods embedded in the collagen matrix [2]. HAP is commonly employed as a coating for bionert metallic and ceramic substrates, such as titanium and alumina [3, 4]. Dense HAP ceramics can serve as bone substitution, which require their good mechanical properties. Therefore, especially required is the HAP powders which exhibit desired characteristics such as small grain size with narrow size distribution and high specific surface area. According to the previous literatures, a number of methods have been proposed for preparing HAP, such as wet chemical routes based on precipitation at low temperature [5, 6], hydrothermal methods [7, 8] and solid-state reactions [9] etc. The wet chemical methods usually lead to irregular forms of HAP powders and require complex process control. In recent years, the hydrothermal routes towards the synthesis of HAP nanorods have been reported [7, 8]. In spite of its much particular characters in high-temperature and high-pressure conditions, the hydrothermal synthesis route is relatively complex and reaction time is comparatively long. So some attentions have been switched to seek some new methods. The high-temperature solidstate method has been applied to the synthesis of HAP for the past several decades [9]. Due to its too much energy consumption, complex apparatus and techniques, the solid-state reaction becomes gradually unpopular and unsatisfied. At present, there are many compounds which have been synthesized by solid-state reaction at room temperature, such as oxide, sulfide, carbonate, hydroxide and so on [10–13]. However, the synthesis of HAP nanorods at room temperature is seldom reported until now. Recently, it is reported that HAP nanoparticles have been synthesized by microwavemediated metathesis in room temperature solid-state reaction [14]. Unfortunately, the products obtained only took the form of particles with large size and irregular diameter distribution. Microwave irradiation has particular advantages such as rapid volumetric heat-

Performance characteristics of Li//Li 1± XCoO 2 cells

Lithium cobalt oxides (LiCoO 2) with varying lithium stoichiometries viz., 0.97, 1, 1.03, 1.06 and 1.1 have been prepared by a solid-state high temperature technique. Structural determination of the synthesized powders with X-ray diffraction (XRD) reveals single-phase materials while the surface morphologies investigated with scanning electron microscopy (SEM) indicate different particle orientation with increase in lithium content. Electrochemical galvanostatic cycling studies of the synthesized powders in lithium 2032 coin type cells in the voltage range 3.5–4.5 V suggest that initial capacity fading is minimum in samples with lithium stoichiochiometries of either 0.97 or 1.03 and stable capacities are attained after the initial 10 cycles. The effect of lithium stoichiometry on the performance of LiCoO 2 in a lithium rechargeable cell is presented.

Structural and dielectric properties of Sb-doped PLZT ceramics

Lead Zirconate Titanate (PZT), a member of ABO 3 (A = mono or divalent, B = tri to pentavalent ions) family is a solid solution of lead titanate and lead zirconate ceramics. PZT ceramics with compositions near Morphotropic Phase Boundary (MPB) offer good ferroelectric, piezoelectric and electrical properties. It is well established that the substitution of La 3+ at the Pb site of PZT (PLZT) gives improved optoelectronic and piezoelectric properties of the materials. In most of the complex PLZT compounds (by increasing the La content in Zr or Ti rich compounds) broadened dielectric peaks or diffuse phase transitions with relaxation character in the transition temperature have been observed. For better understanding of the diffuse phase transition on double doping at the Pb site of PLZT near the MPB and the changes in physical or device parameters, we have carried out systematic studies on structural and dielectric properties of the compounds. In this paper, we report the study of the effect of paired dopants (La and Si) in PZT ceramics. Samples of Sb-doped PLZT were synthesized by high-temperature solid-state solution reaction technique. Preliminary crystal structure and microstructure of the compounds were studied by X-ray diffraction technique. Detailed dielectric studies of the samples suggest that they undergo ferroelectric paraelectric diffuse phase transition. Temperature dependence of dc resistivity of the compounds exhibits Negative Temperature Coefficient Resistance behavior.

Solid Oxide Fuel Cells

AbstractFor Abstract see ChemInform Abstract in Full Text.

Solid oxide fuel cells.

Despite being first demonstrated over 160 years ago, and offering significant environmental benefits and high electrical efficiency, it is only in the last two decades that fuel cells have offered a realistic prospect of being commercially viable. The solid oxide fuel cell (SOFC) offers great promise and is presently the subject of intense research activity. Unlike other fuel cells the SOFC is a solid-state device which operates at elevated temperatures. This review discusses the particular issues facing the development of a high temperature solid-state fuel cell and the inorganic materials currently used and under investigation for such cells, together with the problems associated with operating SOFCs on practical hydrocarbon fuels.

Evidence for significant granite space creation by the ballooning mechanism: The example of the Ardara pluton, Ireland

The emplacement mechanism of the Ardara granite (a Caledonian pluton located on the northwestern seaboard of Ireland) has been a widely cited and a key point of reference in the debate about the granite space problem for nearly half a century. Early models related its subcircular tailed shape, concentric foliation pattern, and concentrically deformed envelope to diapirism. It was subsequently reinterpreted, using strain data, as a ballooning pluton that was created by ∼70% in situ expansion at the emplacement site and was later cut by a regional shear zone. Recently it was the leading example in a wide-ranging review of forcefully emplaced plutons of this type and was reinterpreted as a series of nested diapirs associated with only modest amounts (30%) of forceful space creation, but a large component of inferred early block stoping. We report the results of the complete remapping and extensive collection of new structural data from this 8-km-diameter, normally zoned, three-phase, calc-alkaline pluton. We confirm the existence of the steeply inclined internal foliation pattern and that it was formed in the magmatic state, although this and the outline of the pluton are modified by late-stage (high temperature solid state) regional transcurrent shear zones along two of the pluton contacts. Structural mapping has failed to identify a macroscopic lineation in the magmatic foliation planes, and this is confirmed by strain determinations (using mafic enclave populations and magmatic crystal separations) for the magmatic state deformation that show nearly pure flattening type strains (K = 0). Strains measured by these techniques show an apparently smooth gradient increasing outward toward the pluton contacts from an inner low-strain zone. We argue that these features, together with the simple normal petrographic zonation, a lack of small-scale structures that would indicate the pluton had moved up relative to the wall rocks, and an exposure level that is not in the roof zone, are inconsistent with diapirism (either singly, or multiply) but are most easily explained by a ballooning emplacement mechanism. Synmagmatic shear-sense data from both the pluton and the adjacent country rocks indicate, however, that within the overall context of radial ballooning there was a limited amount of late-stage nonradial (northward) injection of magma. An inversion of the deformed enclave and crystal spacing strain determinations and strain determinations within the country rocks suggest that more than 80% of the volume of the pluton was accommodated by the ballooning mechanism.

Thermophysical properties of gamma-irradiated LaFeO3 and YFeO3 orthoferrites

In the present work, LaFeO3 and YFeO3 orthoferrites were carefully prepared using the solid state high temperature ceramic and sintering technique. On these two materials, numerous measurements were applied before and after γ-absorbed dose (1.24 Mrad) namely, X-ray diffraction (XRD), DC-electrical conductivity, UV/Vis, IR, Mossbauer effect and EPR. Results obtained were explained, interpreted, and discussed in detail on the basis of lattice structure of the new perovskite investigated and the interaction of γ-radiation with the investigated materials. Finally the γ-induced functions are evaluated for electrical conduction, Mossbauer effect and EPR for the first time.

Further investigations on the thermophysical properties of gamma-irradiated urania-doped orthoferrites

(Y1.85−U0.15) FeO3 orthoferrite was carefully prepared using the solid-state high temperature ceramic and sintering technique. On this orthoferrite, numerous measurements have been undertaken before and after 1.24 Mrad γ-absorbed dose, namely X-ray diffraction (XRD), DC-electrical conductivity versus temperature, UV/Vis. absorption, IR absorption, Mossbauer effect (ME) and EPR. In the present work the results obtained were explained, interpreted and discussed in details on the basis of lattice structure of the new perovskite investigated and the interaction of γ-radiation with the orthoferrite lattice.

High-resolution images of ultrafine LiCoO 2 powders synthesized by a sol—gel process

The morphology of ultrafine LiCoO 2 powders prepared by a sol—gel process was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The purity and grain size of LiCoO 2 powders was dependent upon the pH value of the sol—gel process. The grain sizes measured by tapping mode AFM were 68, 74 and 100 nm, for samples made in acidic, neutral and basic media, respectively. Compared with grains synthesized using a solid-state high temperature method, which ranged from 5 to 20 μm, the grains synthesized using a low-temperature sol—gel process were at least 70 times smaller. Only products with small grains made in acidic media displayed a pure LiCoO 2 XRD pattern, implying that growth kinetics were favored in non-acidic media.

Real time X-ray diffraction study of the formation by SHS of the phases γ′ and H in the ternary system Al-Ni-Ti

The formation of two compounds (Al0.20Ni0.75Ti0.05 (γ′) and Al0.27Ni0.50Ti0.23 (H)) of the ternary system Al-Ni-Ti by solid-state high temperature synthesis was investigated by time-resolved X-ray diffraction using a synchroton X-ray beam and a fast detection system to monitor the phase transformations. With a time resolution of 30 ms, it was possible to observe the passage of the combustion front and to know the different steps of the phase formation. These experiments have been completed by electron probe microanalyses of samples in which the reaction had been frozen. They showed concentration gradients and transition states.

Real Time X-Ray Diffraction Study of the Formation by SHS of the Phases γ' and H in the Ternary System Al Ni Ti

The formation of two compositions (Al 0.20 Ni 0.75 Ti 0.05 (γ') and Al 0.27 Ni 0.50 Ti 0.23 (H) in the ternary system Al Ni Ti by solid-state high temperature synthesis (SHS) was investigated. In addition Time-Resolved X-Ray Diffraction (TRXRD) studies were carried out using a synchrotron X-ray beam and a fast detection system to monitor the phase transformations. With a time resolution of 30 ms, it was possible to observe intermediate phases by scattering of the intense X-ray beam irradiating the sample surface during the passage of the combustion front. For the two reactions Ni(Al) was observed before the appearance of the final product. These experiments have been completed by Electron-Probe MicroAnalysis (EPMA) of sample in which the reaction had been stopped. They showed concentration gradients and transitory states. Moreover, we noted for the γ' formation a steady combustion propagation with a great speed while propagation of the combustion front for the H formation was pulsating. Associating these two techniques led to a better understanding of the different phenomena which exist during liquid-solid or solid-solid combustion reaction.

The transition from magmatic to high-temperature solid-state deformation: implications from the Mount Stuart batholith, Washington

Criteria for syntectonic emplacement of plutons are commonly ambiguous. The strongest single criterion is probably the preservation of a continuous transition from submagmatic to high-temperature solidstate deformation. This transition is not commonly documented. An exception is the Mount Stuart batholith, which displays a variety of syntectonic structures within its sheared northeastern margin, including the following: (1) S- C fabrics that range from submagmatic to high-temperature solid-state;(2) solid-state foliation and lineation defined by amphibolite-facies assemblages that overprint and are parallel to magmatic foliation and lineation; (3) folds of magmatic and solid-state foliation that have hinge lines parallel to magmatic and solid-state lineation and to equivalent structures in wall rocks; (4) dikes that were folded and boudinaged over a wide range of rheological states with boudin necks locally filled by tonalite; (5) pegmatite dikes and mineralized joints that are sub-perpendicular to magmatic and solid-state lineation; and (6) submagmatic and high-temperature solidstate ductile shear zones. We suggest that many plutons emplaced during regional deformation do not preserve evidence for syntectonic deformation because of the transitory nature of the submagmatic state and the obscuring effects of postemplacement deformation. Syntectonic features are most likely preserved in plutons cooled at slow to moderate rates, or in plutons deformed at high strain rates during emplacement. The optimum conditions for preservation may occur in plutons emplaced along fault zones in the mid-crust, such as the Mount Stuart batholith, and in intrusions at deeper levels that were rapidly exhumed and/or intruded during the waning stages of regional deformation.

HREM in solid-state chemistry and crystallography

High-resolution electron microscopy has had a great impact on solid state chemistry. The possibility it offers of directly imaging the structure of solids has made it an unvaluable complement to conventional diffraction methods. Disorder and extended effects have become accessible to observation, superstructures, structural modulations and microphases can be identified and particles down to nanometer size can be studied. Combined with electron diffraction and x-ray microanalysis it is a powerful tool for phase analysis, giving guidance to synthesis of new compounds. Under certain conditions even chemical reactions can be studied in situ at atomic resolution. Numerous examples in be found in the fields of high-temperature superconductors, zeolites, ferroelectrics and solid state ionics.