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In this study, QUV accelerated weathering of polyvinyl chloride (PVC) composites with different amounts of titanium dioxide (TiO2) particle was conducted to investigate the effect of TiO2 particle on the surface morphology and the mechanical properties. The results indicate that the surface morphology of PVC without TiO2 particle did not exhibit changes up to 960 h, but exhibited a rough and brittle surface after 1920 h of QUV accelerated weathering. In addition, the tan δ intensity, the elongation at break, and the mean failure energy (MFE) decreased significantly with increasing exposure time due to embrittlement. In contrast, for TiO2 particle-loaded PVCs, no significant influence on the tan δ intensity and the mechanical properties after accelerated weathering were observed, despite the appreciable degradation that occurred in the surface layer. The weatherability, as determined by the mechanical performance, was improved with increasing loading of TiO2 particle in the PVC composites. Although the TiO2 particle in the PVC matrix acts as a photocatalyst to enhance the surface degradation, it is also an effective radiation screener that inhibits embrittlement and retards the decrease in mechanical properties caused by the accelerated weathering process. POLYM. COMPOS., 37:3391–3397, 2016. © 2015 Society of Plastics Engineers

To better understand the oxidation kinetics of Cu, the oxidation kinetics of Cu(111) in the low-temperature range of 313–453 K were studied using spectroscopic ellipsometry. The low-temperature oxidations of Cu(100) and Cu(110) were also investigated and compared against Cu(111). Similar to the kinetics of Cu(111), those of Cu(100) and Cu(110) depend on the oxide thickness, which exhibit logarithmic behavior for oxide thicknesses under 5 nm, cubic behavior in the range of 5–25 nm, and parabolic behavior over 25 nm. A diffusion model was developed to simulate the kinetics of Cu(100), Cu(110) and Cu(111).

Titanium dioxide (TiO2) is the most essential additive in polyvinyl chloride (PVC) matrixes used for outdoor applications. In this study, we primarily investigate the effect of TiO2 on the chemical and molecular changes in PVC sidings during QUV accelerated weathering. The results of this study show that carbonyl and polyene groups were generated on the surface of all of the specimens after 480 h of accelerated weathering but that loading TiO2 into PVC successfully inhibited the increase in the number of these oxidative groups over the entire exposure period compared to PVC without TiO2. In addition, a significant decrease in the number average molecular weight (Mn) and the formation of an insoluble gel were observed for PVC without TiO2 after accelerated weathering. However, the time required for the Mn to decline increased with the amount of TiO2 that was loaded into the PVC matrix, and no insoluble gel was observed during weathering. Furthermore, the crystallinity of PVC without TiO2 increased noticeably after 1920 h of accelerated weathering, whereas no significant change was observed in the crystallinity of PVC with TiO2. These results demonstrate that simultaneous chain scission and crosslinking reactions occurred in PVC without TiO2, whereas only chain scission occurred in PVC containing TiO2. In addition, the chain scission of PVC without TiO2 was initiated earlier than for PVC with TiO2, producing shorter and more mobile chains that underwent secondary crystallization. Accordingly, TiO2 acted as a UV absorber and a radiation screener such that the probability of chain scission was reduced for TiO2-loaded PVC sidings.

Physicochemical analysis in the microscopic sense is a critical assessment of monitoring the polymeric materials under a weathering test, and it links the accelerated laboratory test with the outdoor performance results for a long-term durability. Here, by taking an experimented example for vinyl siding after an outdoor weathering test in Okinawa, Japan for 17 years and a QUV accelerated weathering test for 2880 hours, it was observed that there were entirely different results on the functional groups and the surface image with the atom concentration measured by the attenuated total reflectance Fourier transform infrared and scanning electron microscopy with energy dispersive spectroscopy, respectively. Furthermore, the optimal conditions of a specified accelerated weathering test based on a replication of the natural weathering characteristics are deliberated, thus correcting the deterioration factors configuration in consideration for the physicochemical degradation of a specific material. The aim of this study places an emphasis on the crucial points for improving the accelerated weathering test through a physicochemical analysis.

Low-temperature oxidation of a copper single crystal, Cu(1 1 1), was investigated using an in situ spectroscopic ellipsometer. The oxidation rate followed the cubic rate law at 5–25 nm oxide thickness; thus, the rate law of Cu single crystal oxidation depended on Cu oxide thickness. Furthermore, the activation energy was found to be close to that of grain boundary diffusion of metal ions in the oxide layer. These results could be explained by grain boundary diffusion and oxide grain growth. Thus, we verified that the low-temperature oxidation kinetics of copper depend on oxide grain growth.

Wide-bandgap II–VI compounds are been applied to optoelectronic devices, especially light-emitting devices in the short-wavelength region of visible light, because of their direct gap and suitable bandgap energies. Many methods have been extensively applied to grow high-quality films and bulk single crystals from the vapor and liquid phases.

Owing to their suitable band gaps and high absorption coefficients, Cd-based compounds such as CdTe and CdS are the most promising photovoltaic materials available for low-cost high-efficiency solar cells. Additionally, because of their large atomic number, Cd-based compounds such as CdTe and CdZnTe, have been applied to radiation detectors. For these reasons, preparation techniques for these materials in the polycrystalline films and bulk single crystals demanded by these devices have advanced significantly in recent decades, and practical applications have been realized in optoelectronic devices. This chapter mainly describes the application of these materials in solar cells and radiation detectors and introduces recent progress.

We fabricated pn -junction diodes by thermal diffusion of Ag acceptor into n -type melt-grown Mg 2 Si single-crystalline substrates (electron concentration=2×10 15 cm −3 ) to investigate the infrared photoresponse of the material. The estimated hole concentration at the p -side of the diode diffused with Ag at 550 °C was 3×10 18 cm −3 . Current–voltage measurement of the diodes showed sound rectifying characteristics even at 300 K. A clear photoresponsivity with a photon energy threshold of approximately 0.6 eV was observed from the diode, showing promise for application in infrared light detection devices at wavelengths of 1.2–2 μm.

Efficient low-cost processes for solar-grade Si production are needed to overcome the deficiency in the supply of Si. We have demonstrated a new method for the purification of Si crystal. Low-purity Si powder was dissolved in a Na melt (solvent), and Si grains were crystallized by Na evaporation from the Na-Si solution at 1173 K. Glow discharge mass spectrometry analysis revealed that the concentrations of impurity elements, except Na and B, were decreased in the crystallized Si grain. In particular, the concentration of Fe which was mainly included in the Si powder decreased from 3200 ppm by mass to 1.5 ppm by mass in a refined Si grain. Iron disilicide was crystallized from the solution before the crystallization of Si. It was suggested that impurities were reduced not only by crystallization from the Na-Si melt but also by the dissolution of Si into the melt. Na contaminating the refined Si grain was eliminated down to 0.055 mass ppm by heating at 1723 K under vacuum.

Abstruct An influence of the addition of copper (0.5, 1.0 and 1.5 mass% Cu) on the microstructure andmechanical properties of high purity iron (99.998 mass%) was characterized. The microstructure and microhard-ness of high-purity iron based samples, which were rolled at room temperature and subsequently annealed,were investigated in this work. The microstructure of the samples has been observed by electron back scatter-ing diffraction (EBSD) and the mechanical properties have been studied by using micro-Vickers hardness test.The results of microstructural observation showed that deformation band was formed in high purity iron by roll-ing at room temperature, and it was recovered by annealing up to about 900 K. The microhardness resultsshowed that the softening of high-purity iron occurred by annealing up to about 900 K, while the hardness ofiron added with about 0.5-1.5 mass% copper was kept over 100 Hv and at the early time of annealing reached amaximum. The hardness of iron added with a small amount of copper may be attributed to precipitation harden-ing as well as solution hardening. The orientation of crystal in recrystallized grain was almost same as that ofdeformed grain. (Received November 21, 2011; Revised December 28, 2011; Accepted January 19, 2012)Key words: high purity iron, iron-copper alloy, recrystallization, EBSD, Vickers hardness, annealing, precipitation

The purity is one of the essential factors of the materials for preparing well controlled materials and devices, because the existence of ppm or sub-ppm level impurities leads to a significant and sometimes critical influence on the material properties and devise performance. Since the development of high technology depends strongly on the availability of high purity metals required for fabricating a new functional device, and furthermore, the purity of commercial pure materials for exploratory material researches is insufficient, the purification process that meets any requirements should be developed. In this article, based on our experience, we will describe how to construct the purification process, purification methods, and the purification of iron as an example.

Purification of two kinds of Hf metal, a high-purity Hf (HP-Hf) with 99.7 mass% and a low-purity Hf (LP-Hf) with 98 mass%, by hydrogen plasma arc melting (HPAM) has been carried out and the removal behavior of various impurity elements has been examined. Many metallic impurities (Fe, Al, Cr, Cu, Mn, Sn, Ti etc.) in the melted Hf, with higher vapor pressures than that of Hf, were removed to the very low levels by vaporization during HPAM and their removal rates increased with the hydrogen content of plasma arc. Then, the purity (except for Zr, O, N and C) of LP-Hf and HP-Hf were improved to nearly 99.998% and above 99.999%, respectively, after 60 min of 20%H2+Ar plasma arc melting. For the removal of Fe, Al, Cu and Ti from Hf, the refining effect of HPAM under atmospheric pressure was found to be superior to that of EBM under high vacuum. Therefore, HPAM has been confirmed to be a very useful method for the purification of Hf and the dissociated and activated hydrogen atoms formed in the high temperature plasma arc must play an important role for the unique refining process of HPAM.

Surface tension of liquid iron is an important property for process simulations evaluating Marangoni flow in the melt. In this study, we succeeded to measure accurate surface tension of liquid iron under various oxygen activities and temperatures with overcoming experimental difficulties through the following attempts: (1) To prevent chemical contamination of sample, an oscillating droplet method using an electromagnetic levitator was employed. Surface oscillation frequencies were determined with taking into account sample rotation. (2) To control the oxygen activity of liquid iron, a gas-liquid equilibrium method using CO/CO2 containing gas mixtures was employed. This method enables precise control of oxygen activity with keeping carbon activity low, and therefore, oxygen activity dependence of surface tension was clarified without carbon effect. (3) To measure the surface tension for higher oxygen activities up to the Fe/FeO equilibrium, high-purity iron (99.9972 mass%) was used. Otherwise, minor reactive impurities in the melt such as aluminum are oxidized, which affects the surface tension measurement. Based on the experimental data, the surface tension of liquid iron was expressed as functions of oxygen activity and temperature using the Szyszkowski model. In addition, thermodynamic properties on the oxygen adsorption reaction and structure of the adsorbed oxygen layer on the melt surface were also discussed.

ZrO2 dielectric layers were prepared by a two-step process, a deposition of pure Zr film with and without a negative substrate bias voltage and a subsequent oxidation of the Zr films. We focused on the effect of the negative substrate bias voltage on the Zr film deposition and the subsequent oxidation of the Zr films. As a result, the Zr film deposited at the substrate bias voltage of −50 V (Vs = −50 V) was found to have a high intensity peak of Zr (100) and a uniform and smooth surface. From the capacitance-voltage and current-voltage measurements of the ZrO2 films, a high dielectric constant of 21 and the equivalent oxide thickness (EOT) of 2.6 nm were obtained on the oxidation layer of the Zr film deposited at Vs = −50 V. On the other hand, a low dielectric constant of 15 and the EOT of 3.6 nm was obtained on that of the Zr film deposited at Vs = 0 V. The leakage current density of the ZrO2 film (Vs = −50 V) was 5.69×10−4 A/cm2, and this value was much lower than the 1.21×10−4 A/cm2 for the ZrO2 film (Vs = 0 V). It was found that the two-step process by subsequent oxidation after film deposition using a negative substrate bias voltage is useful for obtaining high-quality dielectric layers.

Hydrogen plasma arc melting (HPAM) of commercial Ti sponges (> 99.7%) was examined. Ti sponges had main impurities such as Fe, Al, Cl and Mn. These main impurities could be reduced more efficiently by HPAM than by Ar PAM. Other small amount of impurities also had a tendency of reduction by HPAM. In addition, it was found that each removal degree is attributable to a differential refining effect caused by the difference of initial impurity concentration. For the unique refining effect of HPAM, dissociated and activated hydrogen atoms involved in the high temperature plasma arc are considered to play an important role in the melting process.

The chromatographic separation of the impurities Ce, Pr, Nd, Sm, Zn, Al, Ca, and Fe from La was investigated using bis(2-ethylhexyl)phosphoric acid (D2EHPA)-impregnated resin as the stationary phase. The distribution coefficients of the study elements as a function of the concentration of the HCl solution were obtained by batch experiment and their separation factors were evaluated based on the distribution coefficients in order to estimate the potential for separation from La. The chromatographic separation revealed that only La is eluted with 0.15 M HCl. The optimum conditions for separation at the room temperature are as follows: a resin bed with a height of 180 mm and diameter of 25 mm; 1800 mL of 0.15 M HCl solution as an eluent; and a flow rate of 1 mL min −1 . It was confirmed that the impurities Ce, Pr, Nd, Sm, Zn, Al, Ca, and Fe were eliminated completely from La when the recovery yield of La was 90%.

Characteristics of the indium tin oxide (ITO) thin films fabricated by a direct printing method were investigated. For the direct printing, 30 mass% ITO ink was formulated by dispersing ITO nanoparticles of less than 10 nm in diameter into alcohol based solvent with additives. Then, the ITO ink was printed onto a glass substrate, which was followed by the heat treatment at 350, 400, 500 and 600°C to fabricate the sintered films. Then, cross-section of sintered film was observed. As a result, the ITO thin film showed porous nanostructure. Also, sheet resistance of the ITO thin film decreased with increasing heating temperature. The decrease of the resistance was attributed to the improvement of carrier concentration in the ITO thin film. In the meanwhile, the optical transmittance increased in proportional to the heating temperature. In case of the ITO thin film heated at 600°C, the improved characteristics of the electrical resistance and the optical transmittance were achieved as 2.19 × 10 3 Ω/sq and 78.6%, respectively.

Lotus-type porous iron rods were fabricated by continuous zone melting technique under the pressure of 2.5 MPa of hydrogen, using iron with three different purities: 99.5%, 99.9% and 99.999%. It was found that the pore size in lotus iron with high purity (99.999% pure) is much larger than that in lotus iron with lower purity (99.5% and 99.9% pure), while the porosity in lotus iron with high purity is lower than that in lotus iron with lower purity. The transfer velocity does not affect the porosity in all lotus iron, but may affect the pore size; the pore diameter decreases with increasing transfer velocity. Thus, it is apparent that the purity of iron significantly affects the pore morphology and the impurities in iron serve as the nucleation sites of pores to increase the pore number density and also suppress the growth of pores due to slower diffusion of hydrogen. [doi:10.2320/matertrans.M2010219]

High-purity Co was prepared with valence-controlled anion-exchange separation, oxidation refining using plasma arc melting, and H2-Ar plasma arc melting on a pilot scale. The result of a laboratory-scale experiment indicated that the slower flow rate is more effective to remove the impurities by anion-exchange separation. However, the separation efficiency is reduced by scaling up the column from the laboratory to pilot scale. The discussion of the decrease in the separation efficiency implies that the distribution coefficient increases as the concentration of the adsorbate is lowered, but a reduced slower flow rate might increase the final purity of Co. In addition to anion-exchange separation, Co oxidation refining using plasma arc melting was useful. Consequently, a high-purity Co of 99.9998 pct by mass excluding gaseous elements was prepared, which represents the highest purity reported.

Pt thin films were deposited on Si substrates by applying a negative substrate bias voltage using a non-mass separated ion beam deposition method. The effect of the substrate bias voltage on the properties of the deposited films was investigated. In the case of Pt thin films deposited without the substrate bias voltage, a columnar structure and small grains were observed. The electrical resistivity of the deposited Pt films was very high (49.3 ± 0.65 µΩ cm). By increasing the substrate bias voltage, no clear columnar structure was observed. At the substrate bias voltage of − 75 V, the resistivity of the Pt film showed a minimum value of 16.9 ± 0.2 µΩ cm closed to the value of bulk (10.6 µΩ cm).

Purification of a 4N grade Cu rod by argon plasma-arc zone melting (APZM) was carried out. Detailed impurity analysis of the Cu rod was performed using glow discharge mass spectrometry (GDMS). Three impurity behavior groups based on segregation and evaporation during APZM were discussed using the GDMS analysis. Although the impurities with segregation coefficient kℴ 1 had no significant reduction in their impurity concentrations. Some impurities, like Mg, S, Cd and Zn, were reduced much faster than the others in Cu. This was ascribed to the removal by zone refining coupled with the evaporation of impurities for Pimp/PCu > 102.

High-purity Fe was manufactured using anion-exchange separation (AES), oxidation refining, and hydrogen-argon plasma arc melting. As a result, the purity of Fe achieved 99.9993 mass pct. Two issues have been improved: the decrease in the refining efficiency in AES was solved by the decrease in the flow rate, and W contamination during plasma arc melting was solved by the increase in the cooling efficiency of W-ThO2 cathode.

The high-quality ZnO single crystals were grown by seeded chemical vapor transport (CVT) in a newly designed ampoule using carbon as a transport agent. The well-faceted crystal of about 5×5×5 mm 3 can be grown reproducibly. Secondary ion mass spectroscopy (SIMS) analysis, X-ray rocking curve (XRC) and photoluminescence (PL) measurements demonstrate that the grown single crystal is of high purity and high crystallinity.

Zinc oxide (ZnO) single crystal was grown, for the first time, by the self-flux method using a high-purity zinc solvent saturated with oxygen. ZnO crystals were successfully grown in the solvent by moving a growing crystal slowly, at about 17 mm/day along a temperature gradient (1.5 °C/mm) in a furnace, from 1050 to 500 °C. Hexagonal single crystals 1–3 mm in length and 0.5–1 mm in thickness were obtained. Energy-dispersive X-ray diffraction, secondary ion mass spectrometry, and photoluminescence confirmed that the purity and crystallinity of the ZnO crystals grown in this work were high.

Distribution coefficients of La, Ce, Pr, Nd, and Sm on solvent-impregnated resins were determined in hydrochloric acid media for the purpose of La purification. Trialkylphosphine (Cyanex 923), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A), and di(2-ethylhexyl) phosphoric acid (D2EHPA) were used as the extractant for the solvent-impregnated resin in the present work. Separation factors were also obtained in order to estimate the potential for the separation of Ce, Pr, Nd, and Sm from La. We found that the extraction mechanism by which the solvent-impregnated resin works is similar to that of solvent extraction. Separation factors between La and the other light rare earth elements and a high sorption rate indicated that the D2EHPA-impregnated resin is the best adsorbent for purification of La among the three tested solvent-impregnated resins.

Purification of 4N (99.99%) and 6N (99.9999%) purity Cu rods by hydrogen plasma-arc zone melting was carried out. Weight loss in the 4N and 6N Cu rods as a function of number of zone refined passes revealed a higher rate of impurity removal by vaporization in 4N Cu when compared to 6N Cu. Purification effect was studied by analyzing major impurities like Mg, Si, Ca, Ti, Cr, Ni and Fe by O 2 + ions and C, O, As, Cl, P and S by Cs + ion sources using secondary ion mass spectrometry. A remarkable decrease of Si, Ti and Fe impurity concentrations in Cu at x / L = 0.03 after 10 zone passes was observed, but no similar purification effect along the remaining length of the zone refined copper rod was observed. Mg, Se and Ca in the Cu rods were reduced faster by a high evaporation effect due to P i / P Cu > 10 2 . On the other hand, removal of O, C, S and Se was expectedly dominated by vaporization in the form of H 2 O, CH 4, H 2 S, and H 2 Se through thermodynamically favored reactions. The overall segregation rate of the individual impurity elements was decreased with an increase in the purity from 4N to 6N of Cu rods. SIMS analysis of trace impurities was successfully carried out on HPZM Cu for quantitative estimation.

There have been many studies on the modeling of elution and breakthrough curves of ion-exchange chromatography. A precise representation of elution curves using an appropriate mathematical model is significant for the application and expansion of ion-exchange chromatography. The significance of precise modeling particularly increases when the yield and purity of the product are important. However, no previous studies have proposed a model that can perfectly represent experimental elution curves. We investigated the purification of various metals by anion-exchange separation and determined an optimum condition for purification of an element through trial and error. An appropriate model replicating the elution curves accurately is greatly needed to reduce the testing phase. Consequently, this paper proposes a novel model called the plate theory in multi-path mode, in which three virtual paths are assumed. The results show that this model well represents the experimental elution curves. In addition, the model was validated by comparing the distribution coefficients obtained from the fitting results with those determined by previously reported batch experiments.

Removal of non-metallic impurities like O, N, C and S in 4N Cu rods by argon plasma-arc zone melting and hydrogen plasma-arc zone melting was investigated. The experimental results were discussed on the basis of thermodynamic estimation. Substantial removal of these impurities along the length of the Cu rods by argon plasma-arc zone melting was observed and relatively better removal by hydrogen plasma-arc zone melting was found to be due to activated hydrogen atoms. The removal of O, N, C and S was ascribed to the segregation effect as well as evaporation in the form of CH4 ,H 2O and H2S. As a result, it was found that hydrogen plasma-arc zone melting is a better technique to eliminate non-metallic impurities like O, N, C and S in Cu. [doi:10.2320/matertrans.MRA2008205]

The refining effect of Ar/Ar-H2 plasma arc melting (PAM) was investigated and the purity of Ta metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Ta metals were removed by Ar/Ar-H2 PAM, down to a few mass ppm levels, and the purities of respective Ta metals refined by Ar/Ar-20% PAM were improved up to 5N5 (99.9995 %) and 5N7 (99.99972 %). It was also found that the deoxidation reaction under hydrogen plasma condition is enhanced by a remarkable decrease in the oxygen concentration of the Ta metal refined by Ar-H2 PAM.

Oxidation refining of Fe using plasma arc melting, by the addition of iron oxide as an oxidizing agent, has been carried out. In this refining process, an impurity element which has higher affinity for oxygen than iron was expected to be eliminated. As the result, decreases in Si, Mn, Al, Ca, Ga, and Zr were observed and 99.996 mass% of iron could be obtained from 99.93 mass% of electrolytic iron by plasma arc melting under oxidizing conditions followed by argon–hydrogen plasma arc melting. Specifically, the removal of Si was found to proceed by the distribution between in the liquid Fe phase and in the oxide phase. In addition, the relation of Si and oxygen concentration in liquid iron was consistent with the data in the literature.

We intend to search a new method to prepare high-quality and large-size p-ZnSe single crystal. In this study, ZnSe:Li3N single crystal is grown by a vertical Bridgman method using a closed double-crucible. The photoluminescence (PL) spectrum of the as-grown ZnSe:Li3N crystal at 8 K shows very strong donor–acceptor pair (DAP) and very weak exciton emissions. In order to activate doped Li3N, ZnSe:Li3N single crystal is annealed at high temperature in Zn-saturated atmosphere. By selecting suitable annealing conditions, a very strong I1 emission line related to shallow acceptor is observed. The capacitance–voltage (C–V) characteristics indicate that the annealed ZnSe:Li3N single crystal is a p-type conduction. Furthermore, the acceptor concentration and ionization energy are estimated by examining the temperature dependences of the free-to-acceptor (FA) emission, the behaviors of Li and N are investigated, and the new emission at 2.34 eV is discussed.

We focused the effect of a negative substrate bias voltage on the nucleation and growth of Cu films during the initial stage of ion beam deposition. The resultant microstructure of Cu films was observed by atomic force microscopy (AFM). It was found that Cu films with or without a negative substrate bias voltage have a different dependence of nucleation and growth. It was established that the mechanism of nucleation and growth of Cu films is changed to a progressive nucleation and lateral growth by a sufficient migration of adatoms accelerated by applying a negative substrate bias voltage.

The long-term native oxidation of Cu films has been investigated at the nanoscale by angle resolved X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and high-resolution transmission electron microscopy. Cu films with different microstructures and crystallographic textures were deposited by with or without a negative substrate bias voltage of − 50 V. The oxidation rate of the Cu films deposited at − 50 V is much lower than that of the Cu films deposited at 0 V. The electron microscopy observation showed that the Cu films deposited at 0 V have two oxide layers, namely, an outer CuO and an inner Cu2O, whereas the oxide layer of the Cu films deposited at − 50 V consists of only Cu2O layer. The difference of texture between the Cu films deposited at 0 V and − 50 V is found to affect native oxidation behavior. It is also considered that many defects in the Cu films deposited at 0 V provide preferential nucleation sites and subsequent growth, which promotes Cu oxidation. The difference in the oxidation behavior of the two Cu films and high-purity bulk Cu can be mainly explained by the difference in texture and microstructure.

High-quality and large-size ZnSe single crystals doped with arsenic (As) have been grown by a closed Bridgman method. Photoluminescence (PL) spectra show bound exciton emission related to As acceptors and strong donor acceptor pair (DAP) emissions in all As-doped ZnSe. When the doping concentration reaches 5 × 10 18 cm − 3 , two sets of DAPs, namely shallow-DAP (D s AP) and deep-DAP (D d AP), are observed. This indicates that As behaves both as a shallow acceptor and a deep complex donor. By examining excitation intensity dependences of the DAP emissions, the ionization energy of As as a shallow acceptor is estimated to be 108 ± 1 meV, and that of the deep complex donor related to As to be 36 ± 1 meV. Furthermore, the correlations between localization energy and corresponding ionization energy for some acceptors are summarized. The results indicate that these correlations obey Haynes’ rule very well.

Purification of La and Ce by a horizontal plasma arc-zone melting (PZM) with Ar plasma arc heating under atmospheric pressure was examined. A stable molten zone of La and Ce on the water-cooled copper hearth could be maintained and, after zone passes, the segregation of impurities along the bars was recognized. Metallic impurities such as Fe, Cu, Al, and Si moved in the zone direction and decreased efficiently at the head side of the zone-melted bars. Especially, remarkable segregations of those impurities were observed on La. In addition, volatile impurities such as Ca, Mg, Zn, and Mn were reduced to further low levels by vaporization. For non-metallic impurities, O, N, C, and S in Ce, and O and N in La moved in the opposite direction of zoning, while C and S in La moved in the zone direction. Furthermore, nonmetallic impurities were reduced unexpectedly along the whole bar during PZM. Consequently, the purity around the head side of La and Ce bars could be sufficiently increased with PZM.

Indium zinc oxide (IZO) films were deposited as a function of the deposition temperature using a sintered indium zinc oxide target (In 2 O 3 :ZnO = 90:10 wt.%) by direct current (DC) magnetron reactive sputtering method. The influence of the substrate temperature on the microstructure, surface roughness and electrical properties was studied. With increasing the temperature up to 200 °C, the characteristic properties of amorphous IZO films were improved and the specific resistivity was about 3.4 × 10 − 4 Ω cm. Change of structural properties according to the deposition temperature was also observed with X-ray diffraction patterns, transmission electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. IZO films deposited above 300 °C showed polycrystalline phases evolved on the amorphous IZO layer. Very flat surface roughness could be obtained at lower than 200 °C of the substrate temperature, while surface roughness of the films was increased due to the formation of grains over 300 °C. Consequently, high quality IZO films could be prepared by DC magnetron sputtering with O 2 /Ar of 0.03 and deposition temperature in range of 150–200 °C; a specific resistivity of 3.4 × 10 − 4 Ω cm, and the values of peak to valley roughness and root-mean-square roughness are less than 4 nm and 0.5 nm, respectively.

In order to prepare high purity lead iodide (PbI2) single crystals, the starting material-iodine (I) has been purified by the sublimation method, and the PbI2 polycrystalline by the normal freezing method. The purification effect of these methods has been confirmed by evaluating the impurity concentration in ingot by glow discharge mass spectrometry (GDMS) analysis. By comparing the purity of three different starting materials, non-purified iodine+6N-Pb, purified iodine+6N-Pb and commercial 6N-PbI2, PbI2 synthesized by purified iodine in the present experiment has the highest purity. This indicates that these purification methods are suitable. The present research results are expected to prepare high-resistivity PbI2 used in radiation detector. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The annealing effect of H 2 or Ar atmosphere on corrosion resistance (CR) of CuAl alloys with 0.2 wt.% Al (CuAl0.2) was examined through oxidation at 973 K in 0.1 MPa O 2 . For annealing at low temperature of 873 K, Ar atmosphere is more effective for improving CR of CuAl0.2. In the case of higher temperature annealing, the highest CR of CuAl0.2 is observed under H 2 atmosphere at 1173 K with slow cooling. Analysis shows that the protection ability of the Al 2 O 3 surface layer formed during annealing is dependent on the partial O 2 pressure remnant in H 2 or Ar atmosphere.

We have successfully grown high-purity and -quality PbI 2 single crystals by the vertical Bridgman method. The rocking curves of four-crystal X-ray diffraction (XRD) show 120 arcsec in full-width at half-maximum (FWHM). The photoluminescence (PL) spectra at 7.8 K show the resolved intensive exciton emission line and the weak DAP emission band. The deep-level emissions are not observed. The measurement of the electrical and radiographic properties show that Leadiodide (PbI 2 ) single crystal has a resistivity of 5×10 10 Ω cm and imager lag is 8 s, respectively. In order to improve the controllability of crystal growth, PbI 2 single crystals were also grown from a lead (Pb) excess PbI 2 source. The experimental results show very good reproducibility. In addition, the growth models of crystal are proposed, and the growth mechanism is discussed.

Removal of impurities from Cu metal by Ar and Ar-20%H2 plasma arc melting (PAM) has been carried out. Several impurities such as Li, Na, Mg, P, S, Cl, K, Ca, Zn, Pd, Pb and Bi in Cu were efficiently removed when only Ar plasma gas was used. Moreover, removal degrees for the above mentioned impurities were significantly increased after Ar-20%H2-PAM, especially for K, Zn and Pd. It was found that Ar-H2 PAM showed an excellent effect to eliminate impurities with higher vapor pressures than that of Cu metal. [doi:10.2320/matertrans.MRA2008054]

The demand for high-purity Mn is growing in the field of advanced electronics devices. Chromatographic separation using chelating resins is useful for pre-concentration of metal ions prior to the determination of metallic elements by chemical analysis. This separation technique can be applied to the recovery of hazardous substances from industrial waste. In the present study, this separation technique was applied to the purification of Mn for the first time. Separation was carried out in an ammonium chloride medium because Mn can be recovered by electrowinning in the final step. Ammonium chloride added to the electrolyte is useful for improving the current efficiency during electrowinning of Mn. The optimum separation process was examined according to the recovery ratio of Mn and the elimination ratio of each impurity derived from the elution curves.

Dislocations are ubiquitous linear defects and are responsible for many of the properties of crystalline materials. Studies on the glide process of dislocations in bulk materials have mostly focused on the response of dislocations with macroscopic lengths to external loading or unloading. Using in situ transmission electron microscopy, we show that nanometer-sized loops with a Burgers vector of ½〈111〉 in α-Fe can undergo one-dimensional diffusion even in the absence of stresses that are effective in driving the loops. The loop size dependence of the loop diffusivity obtained is explained by the stochastic thermal fluctuation in the numbers of double kinks.

We have investigated the effect of FeSi 2 source purity on the electrical property of β-FeSi 2 grown from solution. A high-purity FeSi 2 source avoided a contamination of Cu and W metals was synthesized by melting a high-purity Fe (5N) and Si (5N-up) in a quartz ampoule. Glow discharge mass spectrometry revealed that the purity of the FeSi 2 source synthesized using 5N-Fe and a quartz-ampoule-melting process is one order of magnitude higher than that of the conventional arc-melted FeSi 2 source using 4N-Fe. The β-FeSi 2 crystals grown using the high-purity FeSi 2 and Zn solvent showed n-type conduction, whereas those grown using the arc-melted FeSi 2 showed p-type. The carrier concentration of the n-type crystals was (4.9–6.3) × 10 18 cm − 3 , which was more than 10 times higher than that of the p-type crystals (5.2 × 10 17 cm − 3 ). From the ICP-MS and SIMS analysis of the grown crystals, we found that dominant impurity concentrations (Cr, Mn, Co, Ni, Cu, Zn and W) in the p-type crystals were higher than those in the n-type ones. Therefore, the p-type conductivity of undoped crystals grown using Zn solvent results from unintentional doping by the high impurity level of the used FeSi 2 source.

We report the characteristics of AlN:Er films that were co-deposited by using AlN, Er, and SiO 2 targets. The PL emission spectra show strong green emissions of Er 3+ ions in AlN:Er films annealed at an optimal temperature of 750 °C, which is attributed to the intra-4 f Er 3+ transitions of 2 H 11/2 → 4 I 15/2 and 4 F 7/2 → 4 I 15/2 . This optimal temperature can activate Er species as an efficient visible luminescence center. High-resolution transmission electron microscopy (HREM) observations showed that the AlN:Er film annealed at 750 °C exhibits the microstructure of AlN nanocrystallites embedded in the amorphous matrix. The occurrence of strong Er 3+ emissions in the amorphous–nanocrystalline AlN:Er films by thermal annealing might contribute to an increased number of excitation Er 3+ centers and the presence of oxygen related to Er 3+ excitation and recombination processes. A distinct visible bluish green emission is also confirmed from the EL device with an amorphous–nanocrystalline AlN:Er active layer.

The purification effect by hydrogen plasma arc melting (HPAM) and the respective probabilities of hydride formation for several metals were investigated. Commercially pure Fe, Cr, Ti, V, Zr, Nb, and Ta metals were melted for 60 min using Ar–30 vol% H 2 plasma gas at 5.3 kPa (Ta at 101.3 kPa). Results showed that the degree of removal of each impurity in the metals increases concomitant with the increased vapor pressure difference between the impurity and the metal. This study further established that addition of hydrogen to the plasma gas increases the metal surface temperature, which is a main reason for the superior purification provided by Ar–H 2 plasma arc melting. Thermodynamic calculations showed that the main part of impurities transfers to the gas phase as atomic species, whereas Sb can predominantly form hydrides over other corresponding atomic species.