Polycrystalline alumina fillets containing various chemical additives were prepared by tape casting for use in bonding trials. Oriented sapphire blanks were edge bonded in a furnace with special fixtures to accurately align and apply a load to the components during heat treatment. This approach is consistent with and builds upon the methods used in the previous edge-bonding studies. Flexure strength of the bonded samples, as compared to monolithic sapphire, was used as the performance metric. Additional bonding runs were carried out using the highest performing fillet composition in order to provide a sufficient number of specimens to conduct a Weibull analysis of the failure probability of the bonded material as a function of applied stress.

A high purity alumina composition containing 3 wt.% SiO2, 0.05 wt.% MgO, and
0.05 wt.% Ti, produced the highest strength bonds. This composition yielded an average fracture strength of 255 MPa (37 kpsi), a Weibull modulus of 8.2, and a characteristic strength of 269 MPa (39 kpsi). These results compare favorably to monolithic sapphire specimens which yielded an average fracture strength of 284 MPa (41 kpsi).

Large-scale GaN nanowires were successfully synthesized through ammoniating Ga2O3/Pd films sputtered on the sapphire substrates. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, photoluminescence and Raman spectrum were used to characterize the specimens. The results demonstrate that nanowires are single crystal with hexagonal wurtzite structure and have good optical properties. Raman scattering appears broadened and asymmetric compared with those of bulk GaN due to its polycrystalline nature. In addition, the growth mechanism of GaN nanowires is briefly discussed.

Controlled and reproducible growth of GaN nanowires is demonstrated by pulsed low-pressure metalorganic chemical vapor deposition. Using self-assembled Ni nanodots as nucleation sites on sapphire substrates we obtain nanowires of wurtzite-phase GaN with hexagonal cross sections, diameters of about 100 nm, and well-controlled length. The nanowires are highly oriented and perpendicular to the growth surface. The wires have excellent structural and optical properties, as determined by x-ray diffraction, cathodoluminescence, and Raman scattering. The x-ray measurements show that the nanowires are under a complex strain state consistent with a superposition of hydrostatic and biaxial components.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

ZnO thin films with thickness around 200 nm were deposited on a-plane sapphire substrates by Chemical Vapor Deposition (CVD) method with a mixed ZnO-powder/C-powder solid source. These films were characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and photoluminescence (PL) spectroscopy. The correlation between surface structural properties of ZnO thin films and their optical signature measured by temperature dependence of PL is investigated for various growth conditions such as flow rate O2 injection gas and growth temperature. At room temperature, the columbic interaction enhanced absorption edge of 3.305 eV of these films was determined by optical absorption measurements.

Naturally modulated structures,films of In2O3(ZnO)5, were epitaxially grown by rf magnetron sputtering on sapphire substrates. The crystallographic and morphological features of the films were characterized by using x-ray-diffraction and electron-diffraction patterns. The deposition of strongly c axis orientated films of In2Zn5O8 was achieved by epitaxy with a self-buffer layer (SBL). A film of In2Zn5O8 of approximately 10 nm in thickness was initially deposited as the SBL. This initial film was annealedin situ for 10–15 min, after which the bulk of the film of In2Zn5O8 was grown. Finally, well-crystallized In2O3(ZnO)5films were obtained by annealing the resultant film at 800 °C. The electrical properties of the synthesized film are discussed in relation to the mechanism by which the modulated In2O3(ZnO)5 structure is formed.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Basal, prism and rhombohedral-plane specimens cut and polished from flame-grown sapphire boules developed fine surface textures during heat-treatment in the range 1700° to 1900°C. Microscopic examinations of such surfaces revealed low-angle grain boundaries, dislocations, and other crystal imperfections. Thermally etched textures apparently were generated by three overlapping processes, namely annealing, etching, and decoration. Thermal etching gave evidence of high-temperature relaxation of residual strain energy introduced at low temperature (analogous to cold work in metals), including that introduced by fracture, microindentation, and cutting and polishing during surface preparation.

Single crystals of Al2O3 (sapphire) were grown from PbO-PbF2 and MoO3-PbF2 fluxes; they varied from flat plates (PbF2-rich melts) to equidimensional crystals (PbO- or MoO3-rich melts). The primary growth planes are basal, first-order rhombohedral, and second-order rhombohedral. The habit change is interpreted on the basis of F- contamination and Pb2+ surface adsorption. Possible ion species in the melts and their relative importance on crystal growth from these systems are discussed.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

We have systematically studied the effects of wet chemical etching and high temperature nitridation on the resulting sapphire surface morphology and chemical transformation. The etching of c-plane sapphire substrates using H2SO4, H3PO4, and a 3:1 H2SO4 :H3PO4 mixture as a function of temperature and etching time was studied and compared with H2 etching at 1100°C and air-annealing at 1400°C. The surface nitridation using NH3 and N2 at 1100°C was studied as a function of NH3 concentration, nitridation time, and surface pretreatment. Atomic force microscopy and x-ray photoelectron spectroscopy were used to study the surface morphology and chemical composition. The detailed surface morphology after chemical etching was a function of the chemical composition and the specific time and temperatures.

The smoothest, pit-free sapphire surface was obtained by etching in pure H2SO4 at 300°C for 30 min. Sulfuric acid etching at higher temperatures or for longer periods generated an insoluble mixture of Al2(SO4)3 and Al2(SO4)3·17H2O crystalline deposits on the surface. Phosphoric acid and the 3:1 H2SO4:H3PO4 mixture etched the sapphire preferentially at defect sites and resulted in pits formation on the surface. The high temperature sapphire nitridation resulted in nitrogen incorporation into the surface. The nitrogen content of nitridation layer depends on NH3 concentration, nitridation time, and surface pretreatment. The nitrogen contents of sapphire treated with H2SO4 and 3:1 H2SO4:H3PO4 are about the same as the as-received sapphire. While the nitrogen content of the air-annealed sapphire is ∼1.6 times higher then the nitrogen content of the as-received sapphire.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

The mechanism of the formation of light-scattering centers in sapphire crystals grown by horizontal directed crystallization in gas atmospheres reducing with respect to the Al2O3 melt was studied. The experimental regularities here significantly differ from those observed upon formation of other conventional defects in sapphire crystals (vacancy pores, gas bubbles, and so on). It is shown that the known formation mechanisms of macroscopic ≥1 mm) inclusions in crystals are not acceptable in this case. Using the model of bulk crystallization is proposed to describe the obtained regularities.

The micro-pulling-down method has been adapted to grow fibers with diameters as small as 150 μm. We describe the use of this method to grow fibers of the oxide eutectic materials Al2O3/Y3Al5O12 and Al2O3/GdAlO3, which have exceptional mechanical properties at high temperature. The “Chinese script” microstructure of Al2O3/Y3Al5O12 is stable and uniform, and varies with the pulling rate in the same way as the conventional lamellar eutectics. The microstructure of Al2O3/GdAlO3 is finer, but less stable and homogeneous, particularly at high pulling rate. Fibers produced at low growth rate exhibited self-cladding by the sapphire phase.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Haze defect in SAPMAC method grown sapphire crystal was studied in detail. It is shown that haze is composed by a large number of CO2 bubbles, and haze always appears in the axis region of the crystal since the bubbles formed in front of the crystallization surface are most always draged to the convection rolls in front of the central part of the crystallizaiton surface by melt and then engulfed by the rolls. Moreover, the effects of pulling rate on the formation of haze were analyzed and means for restraining haze was suggested.

Shaped sapphire crystals were grown from the melt by the Stepanov (EFG) technique. High-temperature vacuum annealing of crystals grown in a reducing atmosphere, performed by employing graphite elements in the heater unit of the crystallization chamber, led to the formation of voids of two different types: (1) well-faceted voids which are the result of vacancy coagulation and (2) pores of irregular form which decorate the subgrain boundaries. The formation of these defects may be prevented by suppressing the interaction between the alumina melt and carbon.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

A solution-precipitation process was used to grow Mg–Al spinel microcrystals at etched pits in a c-axial sapphire single crystal surface. In the proposed innovative growth process, the etched pits function as heterogeneous nucleation points. The quenching and aging treatment causes Mg ions to diffuse into the sapphire crystal, precipitating as microcrystals at the etched pits. We found the precipitated crystals to be Mg–Al spinels with a triangular pyramidal shape.

The optically pumped solid-state laser active element is the most widely used inorganic oxide crystals. This oxide material either garnet or corundum structure is made is called Czochralski crystal growth technique pulling industrial scale preparation. Czochralski growth in the country's most advanced along with the participation of a large size, the key variable is the growth of high-quality oxide crystals is described in this description. Ruby, yttrium aluminum garnet, sapphire crystal growth and description presented in titanium. Composition under ambient atmosphere, the variable crystal growth, crystal type and the impact of individual environmental conditions to be described. Suitability for different oxide Czochralski crystal growth process, the focus is on materials properties, e.g., the phase diagram means (melting consistency), the melting temperature of the crucible material, dopant ions impact, and high temperature melting Body Chemistry discussion.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

A combination of experimental and computational fluid dynamics-based reactor modeling studies were utilized to study the effects of process conditions on GaN nanowire growth by metalorganic chemical vapor deposition (MOCVD) in an isothermal tube reactor. The GaN nanowires were synthesized on sapphire substrates using nickel thin films as a catalyst. GaN nanowire growth was observed over a furnace temperature range of 800–900 °C at V/III ratios ranging from 33 to 67 and was found to be strongly dependent on the position of the substrate relative to the group III inlet tube. The modeling studies revealed that nanowire growth consistently occurred in a region in the reactor where the GaN thin-film deposition rate was reduced and the gas phase consisted primarily of intermediate species produced by the reaction and decomposition of trimethylgallium–ammonia adduct compounds. The GaN nanowires exhibited a predominant growth direction. Photoluminescence measurements revealed an increase in the GaN near-band edge emission intensity and a reduction in the deep-level yellow luminescence with increasing growth temperature and V/III ratio.

Epitaxial lead lanthanum zirconate titanate [PLZT(9/50/50)] thin films were fabricated on various single crystal substrates using the spin coating of metallo-organic solutions. The films were heat-treated at 700 °C for 1 h using the direct insertion method. The films were epitaxially grown with being parallel to the SrTiO3, the MgO, and the sapphire substrates, respectively. The epitaxy of the films was investigated using x-ray diffraction, pole figures, rocking curves, and scanning electron microscopy.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

Sapphire single crystal was grown by micro-pulling and shoulder at cooled center (SAP- MAC) technique and the air bubbles were observed as one of the main defects in the as-grown crystals. Based on the growth parameters,the formation mechanism of the bubbles was discussed in the view of the crystal growth kinetics.It suggests that optimizing the temperature distribution in the furnace, selecting a suitable growth velocity and adopting a slightly convex interface to the melt can effectively reduce the quantity of bubbles.

A model is proposed to account for the changes under ultraviolet illumination of several of the prominent optical absorption bands in neutron irradiated crystalline sapphire. This model, based on both new and previously observed photobleaching and predicted optical anisotropic properties of single and paired anion vacancies, assigns absorption and luminescent bands to specific charge states of anion divacancies.


Tungsten Manufacturer & Supplier: Chinatungsten Online - http://www.chinatungsten.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn