Studies on some physical properties of the K2NiF4 type solid solutions,SrO·Ln1−xSrxVO3−0.1x

Electrical and magnetic properties of the K₂NiF₄ type solid solutions SrO·Ln_1?xSr_xVO_3?0.1x (Ln:Nd, Eu and Gd) were studied in the temperature range 77–300K. The room-temperature conductivity decreased as the Sr²⁺-ion content increased. Both SrO·Nd_1?xSr_xVO_3?0.1x and SrO·Eu_1?xSr_xVO_3?0.1x exhibited a metal-insulator transition at some value of x. At high values of x, SrO·Nd_1?xSr_xVO_3?0.1x and SrO·EU_1?xSr_xVO_3?0.1x both revealed a weak ferromagnetism at low temperatures.     

A Full Compositional Range for a (Ga1‐x Zn x )(N1‐x O x ) Nanostructure: High Efficiency for Overall Water Splitting and Optical Properties

Bulk (Ga_1‐x Zn _x )(N_1‐x O _x ) as a photocatalyst has received increasing attention as a potential solution for the energy shortage challenge; however, its catalytic performance is highly limited by its bulk form. To improve the photochemical potential, the nanoscale form of this multiple‐metal oxynitrides is desirable. In this work, a new type of (Ga_1‐x Zn _x )(N_1‐x O _x ) nanostructure is obtained. Its composition can tuned to the full range (0.18 < x < 0.95). The (Ga_1‐x Zn _x )(N_1‐x O _x ) nanostructure exhibits excellent photocatalytic activity for overall water splitting, and the highest quantum efficiency of (Ga_1‐x Zn _x )(N_1‐x O _x ) is as high as 17.3% under visible light irradiation. Using this new type of (Ga_1‐x Zn _x )(N_1‐x O _x ) nanostructure, the narrowing of the bandgap for (Ga_1‐x Zn _x )(N_1‐x O _x ) is not only due to an increase in the valence band maximum, but it is also related to a decrease in the conduction band minimum.     

New cation-deficient spinel oxides,Mn1−x□xV2−2xMo2xO4 (0⩽ x ⩽ 0.33)

New Mn_1?x□_xV_2?2xMo_2xO₄ (0 ? x ? 0.33) oxides have been prepared by hydrogen-reduction of the corresponding defect brannerite-type Mn_1?x□_xV_2?2xMo_2xO₆ oxide precursors. These solid solutions crystallize in a cation-deficient spinel structure. The cation distribution in these oxides has been determined by X-ray powder diffraction intensity analysis and the results indicate a cation distribution of (Mn_1?x□_x) _t[V_2?2xMo_2x]_oO₄.     

Studies on some physical properties of the solid solutions,Ln1−xSrxVO3−0.1x

The magnetic and electrical properties of the solid solutions, Ln_1?xSr_xVO_3?0.1x (Ln:La, Nd, Eu and Gd) were studied in the temperature range of 77–300K. All the solid solutions examined exhibited a metal-insulator transition at some value of x. La_1?xSr_xVO_3?0.1x was an antiferromagnet at a value of x at a low temperature. Both Nd_1?xSr_xVO_3?0.1x and Eu_1?xSr_xVO_3?0.1x were antiferromagnets having weak ferromagnetism at a low value of x at a low temperature. At a high value of x, three of the above mentioned solid solutions were only paramagnetic in the measured temperature range, as was Gd_1?xSr_xVO_3?0.1x for all values of x.     

Recent progress in research on MgxZn1–xO alloys

Ternary Mg_xZn_1–xO alloys are attracting considerable attention for possible application in optoelectronic devices. Recently, a great deal of research on Mg_xZn_1–xO have been reported by many groups, such as growth and optical properties, phase evolution from hexagonal-phase to cubic-phase with the increase of the Mg concentration, thermal stability of Mg_xZn_1–xO films and heterointerfaces, fabrication of excellent ZnO/Mg_xZn_1–xO heterostructure, quantum well or superlattice and application of Mg_xZn_1–xO material in optoelectronic devices. In this paper, we summarize the recent progress in Mg_xZn_1–xO and the advance in device fabrication.     

Growth and applications of GeSn-related group-IV semiconductor materials

Abstract

We review the technology of Ge_1?xSn_x-related group-IV semiconductor materials for developing Si-based nanoelectronics. Ge_1?xSn_x-related materials provide novel engineering of the crystal growth, strain structure, and energy band alignment for realising various applications not only in electronics, but also in optoelectronics. We introduce our recent achievements in the crystal growth of Ge_1?xSn_x-related material thin films and the studies of the electronic properties of thin films, metals/Ge_1?xSn_x, and insulators/Ge_1?xSn_x interfaces. We also review recent studies related to the crystal growth, energy band engineering, and device applications of Ge_1?xSn_x-related materials, as well as the reported performances of electronic devices using Ge_1?xSn_x related materials.     

The system Eu2O3SrOV2O3 at 1400°C

Phase relations in a portion of the system Eu₂O₃SrOV₂O₃ have been investigated at 1400°C and a reduced pressure (10^?4mmHg). On heating, part of the trivalent vanadium was oxidized to the tetravalent state by atomospheric oxygen. The following ternary-phase solid solutions were identified: Eu_1?xSr_xVO_3?0.1x, SrO·2Eu_1?x?Sr_xVO_3?0.1x and SrO·Eu_1?xSr_xVO_3?0.1x.     

Electrical conductivity of the systems (Rb4−xMx)Cu16I7Cl13 (M=K,Cs), Rb4Cu16(I7−xBrx)Cl13 and Rb4Cu16I7(Cl13−xBrx)

The solid solution ranges in the systems (Rb_4?xK_x)Cu₁₆I₇Cl₁₃, (Rb_4?xCs_x)Cu₁₆I₇Cl₁₃, Rb₄Cu₁₆(I_7?xBr_x)Cl₁₃, and Rb₄Cu₁₆I₇(Cl_13?xBr_x), have been examined and the electrical conductivity has been measured as a function of temperature and composition. In the system (Rb_4?xK_x)Cu₁₆I₇Cl₁₃, room temperature conductivities increase from 0.32Scm^?1 for x=0 to 0.47Scm^?1 for x=0.40. On the other hand, the conductivities of the systems (Rb_4?xCs_x)Cu₁₆I₇Cl₁₃ and Rb₄Cu₁₆I₇(Cl_13?xBr_x) decrease with increasing x. The system Rb₄Cu₁₆(I_7?xBr_x)Cl₁₃ shows no significant change of the conductivity on x.     

Properties of TixC1 − x films coated on molybdenum by magnetron sputtering

Properties of Ti_xC_{1 ? x} (0.3 ? x ? 0.6) films deposited onto molybdenum have been examined as functions of their chemical composition. Ti_xC_{1 ? x} films about 4–6 μm thick were deposited onto a sintered molybdenum substrate at 600 °C by magnetron sputtering. The near-stoichiometric Ti_xC_{1 ? x} (x ≈ 0.5) was found to be the most thermally stable. Titanium excess Ti_xC_{1 ? x} (x > 0.5) loses titanium by evaporation and changes its surface morphology above 1200 °C. However, excess titanium will improve the ductility of deposited films. Strong compressive stress was observed in carbon excess Ti_xC_{1 ? x} (x < 0.5). The carbon excess Ti_xC_{1 ? x} is more resistant against thermal evaporation than the stoichiometric compound. However, enhanced diffusion of molybdenum atoms into the carbon excess Ti_xC_{1 ? x} takes place, with the formation of Mo₂C. This Mo₂C formation nearly prohibits the use of carbon excess Ti_xC_{1 ? x} films coated on molybdenum as the first-wall material in fusion devices.     

Structure and electrical characteristics of Ce4+-doped Ba2In2O5

The In-site of Ba₂In₂O₅ with Brownmillerite structure was partially substituted for Ce⁴⁺ ions in order to examine the doping effect on the order-disorder transition. Ba₂In_{2 – x} Ce _x O_{5 + x/2} (x = 0.1, 0.2, 0.3, 0.5, 1.0, and 1.5) were prepared by solid state reaction. X-Ray diffraction analyses of these powder samples demonstrated that Ba₂In_{2 – x} Ce _x O_{5 + x/2} (x = 0.1 and 0.2) possesses Brownmillerite structure. With increasing content of Ce⁴⁺ ion the crystal system of Ba₂In_{2 – x} Ce _x O_{5 + x/2} (x = 0.3, 0.5, and 1.0) changed to cubic perovskite structure above the order-disorder transition temperature of Ba₂In₂O₅. Arrhenius plots of the electrical conductivities of Ba₂In_{2 – x} Ce _x O_{5 + x/2} (x = 0.2, 0.3, and 1.0) exhibited no discontinuity. These compounds had high transference numbers of oxide ion above 973 k.     

Magnetic properties of (FexV1−x)V2S4 and (FexV1−x)V4S8

Magnetic properties of the systems (Fe_xV_1?x)V₂S₄ and (Fe_xV_1?x)V₄S₈ were studied by magnetic susceptibility and 57Fe Mössbauer effect measurements. In the case of (Fe_xV_1?x)V₂S₄, Nèel temperature (T_N) increases with increasing x. In contrast, T_N of (Fe_xV_1?x)V₄S₈ showed a decrease with increasing x. Mössbauer results showed that Fe in (Fe_xV_1?x)V₂S₄ is in a high spin state (magnetic), while Fe in (Fe_xV_1?x)V₄S₈ is in a low spin state (nonmagnetic).     

De nouveaux semi-conducteurs ferromagnetiques: Les oxynitrures d'europium et de gadolinium Eu2+1−xGd3+xO1−xNx

Oxide nitrides Eu²⁺_1?xGd³⁺_xO_1?xN_x have been prepared with NaCl type structure. At 1850°C their homogeneity range is 0 < x ? 0, 26. They are semiconductors and have a ferromagnetic Curie point greater than that of EuO (for x = 0.10 : ΔE 0.8 eV and T_C = 128 K). Their activation energy decreases as x increases. A similar behaviour but less pronounced has been observed for the oxide nitrides Eu²⁺_1?xEu³⁺_xO_1?xN_x and Eu²⁺_1?xNd³⁺_xO_1?xN_x. The magnetic properties are discussed and compared with those of EuO under pressure.     

Effects of iso-and heterovalent substitutions on the luminescent properties of CdS in the systems Zn, Cd ‖ S, Te and In(III), Cd ‖ S, Te

We have studied the luminescent properties of three CdS-based solid-solution series, resulting from isovalent anion substitution (CdS_1?x Te_x), isovalent cation and anion substitutions (Cd_1?x Zn_xS_1?x Te_x), and heterovalent cation substitution in combination with isovalent anion substitution (Cd_1?x In_2x/3S_1?x Te_x). The last two systems have been studied for the first time. The results demonstrate that red or near-IR lumiescence occurs in the three systems, but CdS crystals codoped with In and Te are more attractive because of the high impurity-related emission intensity at rather low In and Te concentrations.     

Short-range order and melting anomalies in thin films

This paper presents electrical resistivity and superconductivity studies for the B1 (NaCl) structure oxides of titanium, vanadium, and niobium. In samples of nominal composition TiO _x , VO _x , and NbO _x ,x was varied from 0.8 to 1.2. It was found that all three of these oxides exhibit room-temperature electrical resistivities characteristic of metallic behavior. With decreasing temperature, the resistivity drops steeply in the case of NbO _x , but remains steady or rises somewhat in the case of TiO _x and VO _x , depending on the exact value ofx. It is suggested that in TiO _x and VO _x there is a large resistivity component due to scattering of carriers by disordered vacancies. Superconductivity was observed in NbO _x (T _c=1.38 K,x=1.0) and TiO _x (T _c=1.0 K,x=1.07). In the latter case the material showed a well-defined maximum ofT _c as a function of composition, withT _c<0.05 K forx<0.85 andx>1.20. Several VO _x samples remained normal to 0.07 K.     

Improved hydrogen evolution activities under visible light irradiation over NaTaO3 codoped with lanthanum and chromium

Na_1−xLa_xTa_1−xCr_xO₃ and NaTa_1−xCr_xO₃ (x = 0.01, 0.03, 0.05 and 0.10) have been synthesized by a solid state reaction method. These photocatalysts can produce H₂ in the presence of methanol under visible light irradiation (λ > 420 nm). The photocatalytic activities of Na_1−xLa_xTa_1−xCr_xO₃ are much higher than those of NaTa_1−xCr_xO₃, respectively. Especially, the H₂ evolution rate of Na_0.9La_0.1Ta_0.9Cr_0.1O₃ is 2.2 μmol h⁻¹, which is nearly 4 times higher than that of NaTa_0.9Cr_0.1O₃ (0.6 μmol h⁻¹). The improved activities of Na_1−xLa_xTa_1−xCr_xO₃ compared with NaTa_1−xCr_xO₃ can be ascribed to two factors: one is smaller particle size and higher specific surface area which is caused by the doping of lanthanum; the other is that Na_1−xLa_xTa_1−xCr_xO₃ has less Cr⁶⁺, which is induced by codoping of lanthanum and chromium.     

A new interpretation of Legendre's transformation and consequences

The Legendre transformation has found widespread application in thermodynamics, Hamilton‐Lagrange‐mechanics and optics. It attributes the values of the coordinates (x, y (x)) representing the points of a monotonic piecewise smooth functional curve y (x) the slopes m_x (x) = dy (x)/dx and the intercepts y (m_x) of their tangents on the y‐axis. Thus, the initial curve y (x) is represented by the ordered set of all slopes m_x (x) = dy (x)/dx of its tangents together with their intercepts y (m_x) on the y‐axis. It is shown that the transformed or conjugated function must basically be supplemented by a homogeneous linear function of the relevant variable. This is usually neglected in the literature. In addition, a new interpretation of the Legendre transformation is presented and discussed: For this purpose the derivative m_x (x) is considered as the proper initial function and integrated between x₀ and x. This integral is complemented by the integral of x (m_x) ((the inverse function of m_x (x)) over m_x between m_x0 = m_x (x₀) and m_x (x), if m_x (x) and x (m_x) are strictly monotonic. The sum of both integrals yields the “area” (xm_x – x₀m_x0). Legendre's transformation is obtained by reordering the respective terms. The procedure of transformation corresponds to integration by parts. Some examples and consequences of the properties considered are demonstrated and discussed using the simple model of two‐state systems. The general results of the present work remove possible internal inconsistencies in thermodynamics.     

Conductivite ionique dans les systems Na1+xZr2−xLx(PO4)3 (L = Cr,Yb)

Ionic conductivity measurements in the solid solution Na_1+xZr_2?xL_x(PO₄)₃ (L = Cr, Yb) have been carried out. The materials have a Nasicon-type structure in a 0 ? x ? x^max._L range (x^max._Cr = 2.0 and x^max._Yb = 1.9). A small monoclinic distortion appears at low temperature for Na₃Cr₂(PO₄)₃. As in the Na_1+xZr₂P_3?xSi_xO₁₂ system a strong increase of the conductivity with rising x has been observed. The results are discussed in connection with temperature and structural parameters.     

A study on martensitic transformation in Ti50−x/2Ni50−x/2Cu x alloys with X≤10 at%

The effect of Cu additions on the martensitic transformation sequence and temperature in Ti_50–x/2Ni_50–x/2Cu _x alloys with x: 1–10 at% are investigated by ER, DSC, X-ray and IF measurements. Experimental results show that the transformation sequence of Ti_50–x/2Ni_50–x/2Cu _x alloys with x: 1–4 at% proceeding as two-stage B2RB19 transformation on cooling and Ti_50–x/2Ni_50–x/2Cu _x alloys with x=5, 10 at% have no martensitic transformation. The addition of Cu in Ti_50–x/2Ni_50–x/2Cu _x alloys assists the formation of R-phase, a behaviour which is quite different from that in Ti₅₀Ni_50–x Cu _x alloys. Both the Ms and T _R temperatures decrease rapidly with increasing Cu addition in Ti_50–x/2Ni_50–x/2Cu _x alloys with x: 1–4 at%. It is proposed that the Cu+Ni effects on the Ms temperature in Ti_50–x/2Ni_50–x/2Cu _x alloys is similar as Cu +Ni effects in Ti₅₀Ni_50–x Cu _x alloys and as Ni effects in as-quenched Ni-rich TiNi alloys.     

Low temperature synthesis and properties of MgxZn1?x O:Al UV transparent conducting films by ultrasonic spray pyrolysis

Mg _x Zn_1?x O:Al UV transparent conducting films were synthesized by ultrasonic spray pyrolysis at low temperature. Effects of Mg doping content and substrate temperature on microstructure, electrical and optical properties of Mg_xZn_1?x O:Al films were investigated. With increasing Mg content x from 0.1 to 0.4, the preferred orientation of (002) in Mg_xZn_1?x O:Al films became weak and the grains became to lenticular-like. The electric resistivities of Mg _x Zn_1?x O:Al films with x?<?0.2 are lower than those of ZnO:Al films, but it obviously increases with the increase of Mg doping contents when x?>?0.2. Highly preferred orientation of (002) in Mg_xZn_1?x O:Al films has been observed when the substrate temperature is over 450?°C. Though the Mg doping content and substrate temperature have no significant influence on the optical transmission of Mg _x Zn_1?x O:Al films, the band gap increases and the absorption edge systematically shifts towards the shorter wavelength with the increasing Mg doping contents, which indicate that the transparent spectrum range of Mg _x Zn_1?x O:Al thin films extend to the ultraviolet band.     

Synthesis of β-phase Ag1−xCuxI (x = 0-0.5) solid solutions nanocrystals

A series of single β-phase nano-Ag_1−xCu_xI (x = 0-0.5) solid solutions powders were synthesized by wet-chemical-chelating reaction processing and citric acid used as complexing agent. The Ag_1−xCu_xI powders were determined by X-ray diffraction and transmission electron microscopy. It was demonstrated that the crystalline size and lattice parameter of the Ag_1−xCu_xI powders decrease with an increase in the amount of CuI substitution. The copper in the lattice of the Ag_1−xCu_xI can effectively prevent the crystalline growth of the Ag_1−xCu_xI powders and citrate used in the Ag_1−xCu_xI powders synthesized process can accelerate single β-phase crystalline structure formation.