NiO Peak Research Articles

The surfactant-assisted Ni–Al2O3 catalyst prepared by a homogeneous precipitation method for CH4 steam reforming

The surfactant-assisted Ni–Al2O3 catalysts are prepared by the homogeneous precipitation method with a surfactant/Al molar ratio ranging from 0.0 to 2.0. It has been investigated the effects of the surfactant on the physicochemical properties and the catalytic activities of the Ni–Al2O3 catalysts. The BET surface area of the catalysts decreases with increasing the surfactant content. The pore volume and pore size of the catalysts increase with increasing the surfactant content. XRD results indicate that all of the catalysts exhibit strong diffraction peaks corresponding to NiO and weak peaks corresponding to NiAl2O4. In the TPR results, the reduction peaks which indicates that the Ni particles strongly interacted with the support are present at between 668 and 688 °C. The activities of the prepared catalysts for methane steam reforming increase with increasing surfactant content in fresh and poisoned state due to an increase of pore volume and pore size.

Research of Bilayer Stacked Resistance Switching Memory Structure Based on Pt/NiO/TiO2/Pt

The large power consumption and the wide distribution of switching parameters for unipolar resistance switching are major hurdles to non-volatile memory application. In this letter, the stacked structure Pt/NiO/TiO2/Pt was investigated to overcome the mentioned problems. TiO2 thin film was formed on NiO by oxidation of metallic Ti thin film through rapid thermal process (RTP) in oxygen atmosphere. The sharp TiO2 (202) peak and NiO (200) peak observed by the X-ray diffraction measurement. This stacked bilayer structure is favorable for reducing reset current in comparison with single layer structure. This is attributed to a small amount of heat loss during rupturing process of conductive filaments. It is suggested that the conductive filament rupture and rejuvenation was happened at the interface between TiO2 and NiO by controlling switching sequence. Furthermore, the diffused Ti in NiO also can result in stabilization of switching parameters.

Influences of process parameters on texture and microstructure of NiO films

The experimental result shows that the preferred orientations of NiO thin films are closely related to the working pressure of argon. All of NiO(111), NiO(200), and NiO(220) diffraction peaks are observed in the XRD patterns and exhibited random orientation of NiO film when the film is deposited in low Ar pressure of 0.67 Pa. As the Ar pressure is increased to 2.67 Pa, only the NiO(200) peak appears and shows (200)-textured NiO films. However, the lattice parameter of NiO film deposited in high Ar pressure of 2.67 Pa is 0.426 nm, which is much larger than that of the NiO bulk (0.417 nm). The lattice parameter can be reduced by post-annealing the film because the interstitial Ar atoms are released from the NiO lattice, decreasing continuously from 0.423 to 0.417 nm as the NiO films are annealed by rapid thermal annealing (RTA) from 300 to 600 °C.

Effect of Gold Addition on Electrical and Optical Properties of NiO Films by Rf Sputtering

The NiO-Au composite films with Au contents of 0 to 33.7 at.% are deposited on glass substrates. The high electrical resistivity (ρ) of Au-doped NiO films with Au contents below 1.0 at.% is difficlut to measure by four point probe. The ρ value could be reduced to 30.4 Ω-cm as Au content of 1.4 at.% is added into NiO film. It is reduced significantly to 0.375 Ω-cm as Au content is increased to 13.6 at.%. Further increasing the Au content to 33.7 at.%, the ρ value of NiO film is further decreased to 4 x 10-4 Ω-cm. On the other hand, the transmittance of Au doped NiO films also decreases with increasing Au contents. The transmittance for pure NiO film is as high as 96 %. As the Au contents of 1.4, 13.6, and 33.7 % are added into NiO film, they are decreased drastically to 45 %, 20 %, and 9 % respectively. The XRD patterns of Au-doped NiO films with Au content below 9.6 at.% only appear NiO peaks and their (200) peaks shift slightly to low angle as Au content is increased. When Au content is added to above 9.6 at.%, the NiO crystalline become worse. In addition, further increasing the Au content to above 13.6 at.%, the (111) peak of Au also appears in XRD patterns. This indicating that the Au atoms instead of part of Ni atoms results in the enlargement of NiO lattice for Au-doped NiO film with lower Au contents, but large amount of Au atoms are precipitated from the NiO lattice when the content of Au in the NiO film is increased to above 13.6 at.%.

Preparation and Properties of P-Type Transparent Conductive NiO Films

The NiO-Cu composite films with various Cu contents of 0 – 18.17 at.% are deposited on glass substrate. An ultra high electrical resistivity (ρ) is obtained and cannot be detected by four point probe measurement when the Cu contents in the films are lower than 6.97 at.%. The ρ value is reduced significantly to 35.8 Ω-cm as Cu content is increased to 9.18 at.%, and it further decreases to 0.02 Ω-cm when the Cu content further increases to 18.17 at.%. The Hall measurement for all Cu-doped NiO films show p-type conduction. In addition, the transmittance of NiO films also decreases continuously from 96 % to 43 % as Cu content increases from 0 to 18.17 at.%. The XRD patterns of Cu-doped NiO films only appear NiO peaks and the crystallinity of NiO films becomes worse as Cu content is added to above 6.97 at.%. Large amount of lattice sites of Ni2+ ions in NiO crystalline are replaced by the Cu+ ions that leads to p-type conduction and result in the degradation of crystallinity for NiO-Cu composite films having higher Cu content.

Development of Ni–YSZ cermet anode for solid oxide fuel cells by electroless Ni coating

Nickel–Yttria-stabilized zirconia (Ni–YSZ) cermet (ceramic–metal composite) anodes have been prepared from a simple electroless Ni bath without hypophosphite. Ni–YSZ powder having varying amounts of Ni has been prepared. The effect of two different reducing agents has been evaluated with respect to stability of the bath. Hydrazine can be effectively used as a reducing agent up to 30 vol.% Ni. However beyond 30% Ni, the hydrazine bath loses its stability. Formaldehyde is found to be a very effective reducing agent for higher Ni concentration. The Ni–YSZ powder obtained is characterized by SEM and XRD. When the powder is oxidized for calculating actual amount of Ni deposited, it turns to complete green due to the formation of NiO. The XRD results also show distinct peaks of NiO. The powder is pressed and sintered in air and reduced in hydrogen atmosphere to convert NiO back to Ni. The sintered microstructure shows a well-defined network of Ni around YSZ particles and the fracture surface shows porosity. These features indicate the effectiveness of the technique in producing the essential microstructural elements necessary for effective functioning of the anode.

Fabrication of (200)-Textured NiO Films on Glass Substrate Using Radio Frequency Sputtering

The experimental result shows that the preferred orientations of NiO thin films are closely related to the working pressure of argon. All of NiO(111), NiO(200), and NiO(220) diffraction peaks are observed in the XRD patterns and exhibited random orientation of NiO film when the film is deposited in low Ar pressure of 5 mTorr. As the Ar pressure is increased to 20 mTorr, only NiO(200) peak appears and shows (200)-textured NiO films. However, the lattice parameter of NiO film deposited in high Ar pressure of 20 mTorr is 0.424 nm, which is much larger than that of NiO bulk (0.417 nm). The lattice parameter can be decreased by post-annealing the film due to the interstitial Ar atoms are released from the NiO lattice and it reduces continuously from 0.423 to 0.417 nm as the NiO films are annealed from 300 to 600 °C. Therefore, post-annealing the NiO film deposited in higher Ar pressure will reduce the lattice misfit between the NiO and L10 FePt film that is beneficial to improve the perpendicular magnetic anisotropy of FePt film.

Performance of Pd catalysts supported on nanocrystalline α-Al 2O 3 and Ni-modified α-Al 2O 3 in selective hydrogenation of acetylene

Nanocrystalline α-Al 2O 3 and Ni-modified α-Al 2O 3 have been prepared by sol–gel and solvothermal methods and employed as supports for Pd catalysts. Regardless of the preparation method used, NiAl 2O 4 spinel was formed on the Ni-modified α-Al 2O 3 after calcination at 1150 °C. However, an addition of NiO peaks was also observed by X-ray diffraction for the solvothermal-made Ni-modified α-Al 2O 3 powder. Catalytic performances of the Pd catalysts supported on these nanocrystalline α-Al 2O 3 and Ni-modified α-Al 2O 3 in selective hydrogenation of acetylene were found to be superior to those of the commercial α-Al 2O 3 supported one. Ethylene selectivities were improved in the order: Pd/Ni-modified α-Al 2O 3–sol–gel > Pd/Ni-modified α-Al 2O 3-solvothermal ≈ Pd/α-Al 2O 3–sol–gel > Pd/α-Al 2O 3-solvothermal ≫ Pd/α-Al 2O 3-commerical. As revealed by NH 3 temperature program desorption studies, incorporation of Ni atoms in α-Al 2O 3 resulted in a significant decrease of acid sites on the alumina supports. Moreover, XPS revealed a shift of Pd 3d binding energy for Pd catalyst supported on Ni-modified α-Al 2O 3–sol–gel where only NiAl 2O 4 was formed, suggesting that the electronic properties of Pd may be modified.

Preparation of Ni/Mg xTi 1 − xO catalysts and investigation on their stability in tri-reforming of methane

Ni/Mg x Ti 1 − x O catalysts were prepared through a wet impregnation method by dispersing Ni on Mg x Ti 1 − x O composite oxides obtained via a sol–gel technique. The Ni/Mg x Ti 1 − x O catalysts were characterized by various means including ICP–OES, BET, XRD, H 2–TPR, SEM, and TG. No free NiO peak was found in all XRD patterns of the Ni/Mg x Ti 1 − x O catalysts. The H 2–TPR and chemisorption results indicated that adding Ti to the NiO–MgO system obstructed the formation of solid solution, and thus increased the reducibility of the catalysts. The prepared Mg x Ti 1 − x O composite oxides had the same ability to disperse Ni as TiO 2 and MgO. The tri-reforming (simultaneous oxygen reforming, carbon dioxide reforming, and steam reforming) of methane over Ni/Mg x Ti 1 − x O catalysts was carried out in a fixed bed flow reactor. The conversions of CH 4 and CO 2 can respectively be achieved as high as above 95% and 83% over Ni/Mg 0.75Ti 0.25O catalyst under the reaction conditions. The activity of Ni/Mg 0.75Ti 0.25O and Ni/Mg 0.5Ti 0.5O did not decrease for a reaction period of 50 h, indicating their rather high stability. The experimental results showed that the nature of support, the interaction between metal and support, and the ability to be reduced played an important role in improving the stability of catalysts.

Structure and magnetic properties of oxygen-stabilized tetragonal Ni nanoparticles prepared by borohydride reduction method

We report a comprehensive study on the structure and magnetic properties of ultrafine Ni nanoparticles prepared by the borohydride reduction method. A spontaneous surface oxide layer of NiO encapsulates the Ni particles, as these have been prepared under ambient atmosphere. From the x-ray diffraction (XRD) pattern, the ``as-prepared'' sample has been identified as Ni in a tetragonal crystal structure, stabilized by the incorporation of oxygen atoms in the Ni lattice. On annealing this sample in air at different temperatures, the XRD patterns showed an interesting feature: unexpected fcc Ni peaks appeared together with the usual NiO peaks. Anomalous behavior is also observed in the $M\text{\ensuremath{-}}H$ curves, with the as-prepared sample showing a linear response with field and low values of magnetization and the annealed samples showing ferromagnetism with large coercivity $(290\phantom{\rule{0.3em}{0ex}}\mathrm{Oe})$ and high magnetization values. These surprising and seemingly contradictory observations have been coherently explained on the basis of a proposed phenomenological model. Furthermore, we attribute the observed low magnetization values of the as-prepared sample to an antiferromagnetic superexchange interaction between some of the Ni atoms, mediated by the dissolved oxygen atoms in the Ni lattice.

Nickel and nickel oxide nanoparticles prepared from nickel nitrate hexahydrate by a low pressure spray pyrolysis

Nickel nanoparticles prepared from Ni(NO 3) 2·6H 2O by using a low pressure spray pyrolysis (LPSP) are reported in this paper. Effects of pressure, carrier gas flow rate, concentration of precursor and type of reducing agents on the size, morphology and crystallinity of nickel nanoparticles were investigated. It is found that pressure and carrier gas flow rate play crucial roles in the reduction of NiO to nickel in the LPSP process. A relatively higher solution concentration is suitable for the generation of nanoparticles. Cosolvents such as, formic acid and ethanol, as well as H 2, were treated as the reductives in the synthesis of nickel (nanoparticles) in this work. Weak NiO peaks, together with strong nickel peaks, in powder XRD patterns, indicated that nickel nanoparticles are easier to be oxidized compared with the submicron-sized one investigated by conventional spray pyrolysis due to their higher surface potential. Another possible reason may come from the incomplete reduction in very short residence time because of the decrease of H 2 amount in some cases. A possible mechanism of nickel nanoparticles formation has been suggested based on the demonstration of our previous research as well.

Nickel and nickel oxide nanoparticles prepared from nickel nitrate hexahydrate by a low pressure spray pyrolysis

Nickel nanoparticles prepared from Ni(NO 3 ) 2 ·6H 2 O by using a low pressure spray pyrolysis (LPSP) are reported in this paper. Effects of pressure, carrier gas flow rate, concentration of precursor and type of reducing agents on the size, morphology and crystallinity of nickel nanoparticles were investigated. It is found that pressure and carrier gas flow rate play crucial roles in the reduction of NiO to nickel in the LPSP process. A relatively higher solution concentration is suitable for the generation of nanoparticles. Cosolvents such as, formic acid and ethanol, as well as H 2 , were treated as the reductives in the synthesis of nickel (nanoparticles) in this work. Weak NiO peaks, together with strong nickel peaks, in powder XRD patterns, indicated that nickel nanoparticles are easier to be oxidized compared with the submicron-sized one investigated by conventional spray pyrolysis due to their higher surface potential. Another possible reason may come from the incomplete reduction in very short residence time because of the decrease of H 2 amount in some cases. A possible mechanism of nickel nanoparticles formation has been suggested based on the demonstration of our previous research as well.

Effect of Deposition Temperature and Post-Heat-Treatment Condition on the Characteristics of (100)-Self-Orientation LaNiO3 Films Prepared by RF Magnetron Sputter Deposition

ABSTRACTLa-Ni-O films were deposited at deposition temperature ranging from 250 to 540°C by rf magnetron sputter deposition. The effects of deposition temperature and the following heat-treatment condition on the constituent phases and characteristics of LaNiO3 films were investigated. LaNiO3 phase was obtained at the deposition temperature of 250 and 360°C, while La-rich phase of La2NiO4 was appeared above 540°C. Crystalline phases of resultant films after the following heat-treatment strongly depended on the partial pressure of oxygen gas in ambience, i.e., in case of the heat-treatment at 800°C, diffraction peaks originated from LaNiO3 phase disappeared on XRD patterns in pure nitrogen gas ambience, while impurity peaks of NiO appeared in oxygen-excess (>50%) ambience. As a result, LaNiO3 films with high crystallinity and the same lattice parameter as the bulk one were obtained in the deposition at 360°C followed by the heat-treatment at 700°C in air.

Exchange coupling of NiO/CoFeB films

The exchange coupling in NiO/CoFeB films was investigated. A unidirectional anisotropy was obtained in films with NiO layer thickness of 30–50 nm. The crystal texture of films and magnetic properties were found to be different when the stacking sequence was reversed. In glass/Cu/CoFeB/NiO films, a strong NiO (1 1 1) peak was observed with increasing NiO thickness and the exchange coupling field was about 30 Oe. On the other hand, in the reversed glass/NiO/CoFeB/Cu films, the intensity of the NiO (1 1 1) peak was much weaker and the exchange coupling field was about 60 Oe. A drastic increase in the coercivity was also observed.

X-ray absorption fine structure and neutron diffraction analyses of de-intercalation behavior in the LiCoO 2 and LiNiO 2 systems

Variations of electronic and local structures of Ni and Co in Li 1 − x NiO 2 and Li 1 − x CoO 2 as a function of x were clarified for the first time by in situ X-ray absorption fine structure analysis (XAFS). Chemical shifts of the X-ray absorption near edge sructure spectra of the Ni K-edge in Li 1 − x NO 2 as a function of x were continuous while an abrupt change was observed for the Co K-edge spectra of Li 1 − x CoO. Radial structure functions obtained by Fourier-transform of the Ni K-edge EXAFS of LiNiO 2 exhibited abnormally low height of the Ni-O peak. This phenomenon is explained by the Jahn—Teller distortion of the NiO 6 octahedron due to the low spin Ni 3+ (d 7) ion. De-intercalation of the Li ion caused oxidation of Ni 3+ (d 7) to Ni 4+ (d 6) and reduced the distortion, hence the Ni-O peak increased with increasing x value. The crystal structures of LiNiO 2 treated with D 2O, and electrochemically de-intercalated Li 0.34NiO 2 were solved by Rietveld analysis of neutron diffraction data.

Domain structure in NiO biasing layers (abstract)

Fe3O4/NiO multilayers exhibit long-range antiferromagnetic order with the magnetite ferrimagnetic correlations confined to a single layer due to stacking faults of the spinel structure at the interfaces. We are studying the field dependence of the interlayer coupling and magnetic structure in a series of Fe3O4/NiO multilayers using neutron diffraction. Both NiO and Fe3O4 thin films were included in the measurements for comparison. In a single thick Fe3O4 film, intensity changes with magnetic field are consistent with the alignment of the net ferrimagnetic moment parallel to the applied field. In a single thick NiO film, we observe no intensity changes with magnetic field. For multilayers where the ratio of NiO to Fe3O4 is far from unity, the field dependence approximates that of the thick film of the majority constituent. However, for a Fe3O4 (68 Å)/NiO (34 Å) multilayer the NiO antiferromagnetic intensity decreases with increasing field, applied parallel to a [110] axis in the film plane. This indicates a domain repopulation in the NiO, concomitant with the magnetization of the magnetite, where the antiferromagnetic modulation direction prefers the [111] axes that are closest to the applied field direction. A broadening of the NiO peak shows that the repopulated domains are smaller. We are pursuing a complete measurement of the domain populations by measuring a series of NiO antiferromagnetic diffraction peaks.

Rapid Preparation of Ferrite Films by Plasma-Enhanced MOCVD

Oxide thin films of composition Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-x-y</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (0≤x+y≤1.0) were prepared at high deposition rates of between 200 and 300 nm/min by plasma-enhanced MOCVD from a gas mixture containing Fe(C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , Zn (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , Ni(C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , at an rf power of 400 W or higher and a temperature of 600°C under a high flow-rate for the source vapors (e.g. 2.35×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> mol/min for the Fe source). The X-ray diffraction patterns of the films indicated that Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (0≤x≤0.8), Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-y</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (0≤y≤1.0) and Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> films consisted of only a spinel phase with good crystallinity. However, a small NiO (111) peak was observed together with the spinel peaks in the diffraction pattern of the Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.0</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> film. SEM images of the films showed that they had densely columnar structures, irrespective of their compositions.

Field-Induced Decoupling of NiO-Magnetite Multilayers

ABSTRACTNiO-magnetite multilayers exhibit long range antiferromagnetic order with the magnetite ferrimagnetic correlations confined to a single layer due to stacking faults of the spinel structure at the interfaces[l, 2, 3, 4]. A systematic study of the field-dependence of the interlayer coupling in a series of NiO-magnetite multilayers has been made using neutron diffraction. Both NiO and magnetite single thin films were included in the measurements for comparison. In the magnetite film, intensity changes with magnetic field are consistent with domain reorientation of the net ferrimagnetic moments, while in the NiO film there are essentially no intensity changes. There is no significant field dependence of the magnetic correlation lengths in either film. For multilayers where the ratio of NiO to magnetite layer thickness is far from unity, the field dependence approximates that of the bulk films. However, for a Fe3O4(68Å)|NiO(34Å) multilayer the NiO antiferromagnetic intensity decreases with increasing field, and there is a broadening of the NiO peak on the order of 30 percent. Concomitantly, the magnetite spins rotate collinear with the field, as expected, due to the net 4.2 μB moment per unit-cell. The NiO moments appear to rotate into domains where the direction of propagation of the ferromagnetic sheets is closer to the field direction.

Composition profile across a NiO/Ni interface determined from Auger electron peak shape analysis

AbstractThe composition depth profiles of NiO layers grown on Ni metal were determined by AES and ion beam etching. As the shape of the Ni peak varies significantly with composition, a simple peak‐to‐peak (p‐p) analysis seems not to be applicable. Therefore the complete peak shape at any point of the profile was fitted by a superposition of a metal and an oxide peak. From the fit, the NiO content in the Ni matrix can be determined. Thus a quantitative analysis can be provided from the peak shapes. In addition to the more rigorous treatment, formulae for the p‐p amplitude have been developed which allow for the superposition of Ni and NiO peaks. Then an analysis can also be obtained with reasonable accuracy using the p‐p amplitudes only. The methods can be applied in materials where the peak shape changes due to a superposition of peaks.

Influence of coordination preference of cations upon the formation and the color development of tin spinels

Cobalt-substituted 2MgO⋅SnO2, xCoO⋅(2-x)MgO⋅SnO2, reveals brilliant blue, socalled cerulean blue. On the contrary, cobalt-substituted 2ZnO⋅SnO2, xCoO⋅(2-x)ZnO⋅SnO2, reveals greyish green. In cobalt-substituted NiO⋅MgO⋅SnO2, xCoO⋅(1-x)NiO⋅MgO⋅SnO2, blue colors develope, while in cobalt-substituted NiO⋅ZnO⋅SnO2, xCoO⋅(1-x)NiO⋅ZnO⋅SnO2, bluish green colors.To observe the influence of tetrahedral and octahedral preference of cations such as Mg2+, Zn2+, Co2+, Ni2+ and Sn4+ upon the formation and the color development of the tin spinels, the gradual substitution of Zn2+ for Mg2+ of the spinels in CoO-MgO-SnO2, NiO-MgO-SnO2 and CoO-NiO-MgO-SnO2 systems was carried out. On samples prepared by calcining the oxide and basic carbonate mixtures at 1300°C for 1 hour, the reflectance between 400-760mμ was measured by self-recording spectrophotometer, and the X-ray analysis was also carried out to observe the spinel formation and calculate the lattice constant. The results were summarized as follows.1. CoO-MgO-ZnO-SnO2 system.All samples prepared according to 0.2CoO⋅(1.8-x)MgO⋅xZnO⋅SnO2, 0.5CoO⋅(1.5-x)MgO⋅xZnO⋅SnO2 and CoO⋅(1-x)MgO⋅xZnO⋅SnO2, revealed the formation of single spinel. In these systems, in the case of x=0, fresh blue developed, giving deep absorption characteristic of tetrahedral Co2+ ions at about 550-680mμ. But with increasing the amount of x, the absorption in this region became shallow to some extent, while the absorption at about 400-540mμ became deep. Therefore color changed from blue to greyish green in Zn2+ ion-rich region, showing the absorption of octahedral Co2+ ions owing to the strong tetrahedral preference of Zn2+ ions.2. NiO-MgO-ZnO-SnO2 system.In nickel-substituted 2MgO⋅SnO2, xNiO⋅(2-x)MgO⋅SnO2, the spinel formation became difficult with increasing the amount of Ni2+ ions, owing to the lack of cations occupying the tetrahedral interstices. (Ni2+ and Sn4+ ions have octahedral preference and Mg2+ ion also seems to be the same because MgO is of rock salt type.) NiO⋅MgO⋅SnO2 was identified by X-ray analysis to be composed of no single spinel, but a mixture of SnO2, NiO-MgO solid solution and spinel. Only the diffraction peaks of NiO and SnO2 were observed in the calcined sample of 2NiO⋅SnO2. In this system zinc-substituted NiO⋅MgO⋅SnO2 was prepared according to NiO⋅(1-x)MgO⋅xZnO⋅SnO2. The spinels were obtained in the range of x≥0.5. The color became some what bluish in the case of x=0.5, owing to the absorption of tetrahedral Ni2+ ions, In Zn2+ ion-rich region however, this absorption diminished, and in NiO⋅ZnO⋅SnO2 only the absorption of octahedral Ni2+ ions was observed.3. CoO-NiO-MgO-ZnO-SnO2 system.Samples with the composition of 0.1CoO⋅0.9NiO⋅(1-x)MgO⋅xZnO⋅SnO2, 0.2CoO⋅0.8NiO⋅(1-x)MgO⋅xZnO⋅SnO2 and 0.5CoO⋅0.5NiO⋅(1-x)MgO⋅xZnO⋅SnO2 were prepared. Cobalt-substituted NiO⋅MgO⋅SnO2,