Constitution of the Ni3Cr-Ni3Al-Ni3W system

Isothermal sections of the Ni-Cr-Al-W system have been investigated at 75 at % Ni and temperatures of 1523 and 1273 K, by means of phase compositional analysis, X-ray diffraction and microscopical examination. The alloys studied lay in the range 2.5 to 10 at % Cr, 12.5 to 20 at% Al, 2.5 to 6.25 at % W, The phases formed were, and the bcc solid solution based on tungsten (designated ₂). The maximum extent of the region was found to be 3 at % each of chromium and tungsten. Preferential partitioning of tungsten to occurred. Study of an Ni-10Cr-12.5Al-2.5W alloy aged at 1273 and 1073 K, after quenching from 1573 K, showed that changes in and compositions and lattice parameters occur as a function of ageing time.     

Perovskite phase formation in the PbMg1/3Nb2/3 O3-PbZrO3-PbTiO3 system by the columbite route

The reaction mechanism of PbMg_1/3Nb_2/3O₃-PbZrO₃-PbTiO₃ (PMN-PZT) perovskite phase prepared by the columbite route has been studied in the temperature range from 600 to 800 °C. The effects of heating and cooling rate during the calcination of 3PbO +MgNb₂O₆+PZT powder mixtures have also been investigated. Nearly pure perovskite phase, 0.9 PMN-0.1 PZTsolid solution with no pyrochlore phase, as determined by X-ray diffraction, could be prepared at 800 °C for 2 H. From DTA/TGA, dilatometry and XRD data the reaction mechanism of PMN-PZT solid solution formation could be divided into three steps: (i) decomposition of columbite (MgNb₂O₆) by reacting with PbO at 350 to 600 °C (ii) the formation of a B-site-deficient pyrochlore phase Pb₂Nb_1.33Mg_0.17O_5.50 at close to 650 °C, and (iii) the formation of perovskite phase PMN-PZT solid solution from the reaction of Pb₂Nb_1.33Mg_0.17O_5.50 pyrochlore phase with MgO and PZT above 650 °C.     

The Ni3Al-Ni3Cr-Ni3Ru section of the Ni-Cr-Al-Ru system

An investigation is reported of the 75 at% nickel section of the Ni-Cr-Al-Ru system at 1523 and 1273 K. Constitutional data obtained by electron probe microanalysis, X-ray diffraction and microscopical examination are presented as partial isothermal sections. At 1523 K, the major part of the section consists of phase, while the aluminium-rich region contains a and+ region; the extent of the solid solution of chromium and ruthenium in totals ~ 4 at%. The ruthenium-rich corner of the section shows a two-phase region consisting of + ruthenium-rich solid solution. At 1273 K the,+ and + ruthenium regions increase in extent. The/ mismatch values in the equilibrated alloys studied lie in the range ~ –0.08 to –0.39%. Constitutional features of as-cast alloys are also reported.     

The Ni3Al-Ni3Cr-Ni3Mo section of the Ni-Cr-Al-Mo system

An investigation is reported of the constitution of the 75 at % nickel section of the Ni-Cr-Al-Mo system in the temperature range 1523 to 1073 K. Alloys in the region 10 to 20 at % Al were annealed at 1523, 1273, and 1073 K, respectively, and subjected to electron microprobe analysis, X-ray diffraction, and microscopical and hardness examination. Constitutional data are presented as partial isothermal sections and as vertical sections. At 1523 K the section consists only of fields containing ,+ and , the last mentioned phase being predominant. With decreasing temperature the and + fields increase in extent. Also, the NiMo and Ni₃Mo phases were encountered in the ternary Ni-Al-Mo alloy studied. The quaternary + alloys showed small lattice mismatch values, i.e. up to 0.25%. Raft like morphologies of were found in the quaternary alloys, resulting from directional coarsening. Observations of as-cast structures are also reported.     

Phase equilibria in the system LaMnO3 + δ-SrMnO3-LaFeO3-SrFeO3 − d

We have revealed the formation of a continuous series of orthorhombic LaMn_{1 ? y} Fe_yO₃ solid solutions (0<y<1); La_{1 ? x} Sr_xFeO₃ solid solutions in the composition range 0 < x ≤ 0.8, with an orthorhombic structure at 0 < x ≤ 0.6 and a cubic structure at 0.6 < x ≤ 0.8; and a tetragonal SrMn_{1 ? y} Fe_yO₃ phase in the range 0.6 ≤ y ≤ 1. The composition stability limits of the perovskite phase La_{1 ? x} Sr_xMn_{1 ? y} Fe_yO₃ have been determined, and the 1100°C isotherm of the La₂O₃-SrO-Mn₃O₄-Fe₂O₃ system in air has been constructed.     

Phase equilibria in the system BaTiO3-BaGeO3

The system BaTiO₃-BaGeO₃ has been investigated by DTA, metallographic and X-ray diffraction methods. A number of selected samples were also analysed on the electron probe micro-analyser. The system was found to be of the simple binary-eutectic type with partial solid solubility at both ends. The eutectic composition was established as 68±0.5 mol% BaGeO₃ and its melting temperature as 1120±5° C. The solid solubility of BaGeO₃ in BaTiO₃ at 1120°C was found to be 1.8 mol % and that of BaTiO₃ in BaGeO₃ 2.2 mol %. Additions of BaGeO₃ to BaTiO₃ did not appear to cause any change in the temperature of the cubic to hexagonal inversion of BaTiO₃ but the temperature of the tetragonal to cubic inversion was raised slightly with such additions. The transformation temperature of 1180° C for the low- to high-temperature form of BaGe0₃ was not affected by additions of BaTiO₃     

On the anomalous CMN-He3 3 thermal boundary resistance

It is proposed that the mechanism of the anomalously high thermal transfer rates observed between CAIN and liquid He³ is simply the electromagnetic dipole coupling between electrons and He³ nuclei. A crude theory based on this assumption explains the observed linear dependence of the Kapitza resistanceR _K onT, the order of magnitude of the coefficient, and the absence to date of the effect in dilute He³-He⁴ solutions. We predict that (1)R _K (T) should go through a minimum at about 1 mdeg, (2)R _K should be decreased by applying a magnetic field, (3) a similar linearT dependence (though with much larger coefficient) should be seen in dilute solutions below 5 mdeg, and (4) a similar, though probably less striking effect, should be observed for ferromagnetic metals in contact with He 3 at sufficiently low temperatures.Supported by Nordita.An up-to-date account of the experimental and theoretical situation regarding this effect can be found in Ref. 1:     

Measurement of the γ-anisotropy in

The study of the radiative neutron capture by protons, n+p→d+γ, provides valuable information about the nucleon–nucleon interaction. So far, no experimental value has existed for the γ-anisotropy which may appear if neutrons and protons both are polarised. A non-vanishing γ-anisotropy η is a clear-cut signal for the existence of transitions ³S₁→ ³d₁ from the triplet initial state to the ground state of the deuteron. We report the first measurement of this observable. The result is η=(1.0±2.5)×10⁻⁴ at 50.5% polarisation of neutrons and protons.     

Solid state reactions in the Fe2O3-CaCO3-In2O3 system

The kinetics of solid-state reactions of powdered reactants were investigated by X-ray and by differential thermogravimetry in a magnetic field. Measurements revealed mutual diffusion of the Fe³⁺ and In³⁺ ions in the Fe₂O₃-In₂O₃ system heat treated for 3 h at 700 to 1400° C. Diffusion of indium into the Fe₂O₃ lattice caused a shift of the Curie temperature of the antiferromagnetic iron oxide towards lower temperatures. Only Caln₂O₄ was found between CaCO₃ and In₂O₃ up to 1400° C. Also, in the Fe₂O₃-CaCO₃-In₂O₃in system, the reaction started with the mutual diffusion of iron and indium and the forming of CaFe₂O₄. End-products were the magnetic -Ca₄Fe₁₄O₂₅ and CaFe₄O₇, and the non-magnetic CaFe₅O₇, depending on the In³⁺ concentration. Indium stabilized the magnetic calcium-iron oxide structures, shifting their Curie temperatures towards lower values.     

Electrical Stress Influences the Efficiency of CH3NH3PbI3 Perovskite Light Emitting Devices

Organic–inorganic hybrid perovskite materials are emerging as semiconductors with potential application in optoelectronic devices. In particular, perovskites are very promising for light‐emitting devices (LEDs) due to their high color purity, low nonradiative recombination rates, and tunable bandgap. Here, using pure CH₃NH₃PbI₃ perovskite LEDs with an external quantum efficiency (EQE) of 5.9% as a platform, it is shown that electrical stress can influence device performance significantly, increasing the EQE from an initial 5.9% to as high as 7.4%. Consistent with the enhanced device performance, both the steady‐state photoluminescence (PL) intensity and the time‐resolved PL decay lifetime increase after electrical stress, indicating a reduction in nonradiative recombination in the perovskite film. By investigating the temperature‐dependent characteristics of the perovskite LEDs and the cross‐sectional elemental depth profile, it is proposed that trap reduction and resulting device‐performance enhancement is due to local ionic motion of excess ions, likely excess mobile iodide, in the perovskite film that fills vacancies and reduces interstitial defects. On the other hand, it is found that overstressed LEDs show irreversibly degraded device performance, possibly because ions initially on the perovskite lattice are displaced during extended electrical stress and create defects such as vacancies.     

Statistical Reason for the 1.5σ Shift

Ever since Motorola, Inc. introduced its Six Sigma quality initiative, quality practitioners have questioned why followers of this philosophy add a 1.5σ shift to the average before estimating process capability. Six Sigma advocates claim such an adjustment is necessary but offer only empirical studies as justification for this decision. By examining the sensitivity of control charts to detect changes of various magnitudes, this article provides a statistically based reason for including such a shift in the process average. A new capability index, called dynamic C_pk, incorporating this shift is introduced.     

Extreme Reconfigurable Nanoelectronics at the CaZrO3/SrTiO3 Interface

Complex oxide heterostructures have fascinating emergent properties that originate from the properties of the bulk constituents as well as from dimensional confinement. The conductive behavior of the polar/nonpolar LaAlO₃/SrTiO₃ interface can be reversibly switched using conductive atomic force microscopy (c‐AFM) lithography, enabling a wide range of devices and physics to be explored. Here, extreme nanoscale control over the CaZrO₃/SrTiO₃ (CZO/STO) interface, which is formed from two materials that are both nonpolar, is reported. Nanowires with measured widths as narrow as 1.2 nm are realized at the CZO/STO interface at room temperature by c‐AFM lithography. These ultrathin nanostructures have spatial dimensions at room temperature that are comparable to single‐walled carbon nanotubes, and hold great promise for alternative oxide‐based nanoelectronics, as well as offer new opportunities to investigate the electronic structure of the complex oxide interfaces. The cryogenic properties of devices constructed from quasi‐1D channels, tunnel barriers, and planar gates exhibit gate‐tunable superconductivity, quantum oscillations, electron pairing outside of the superconducting regime, and quasi‐ballistic transport. This newly demonstrated ability to control the metal–insulator transition at nonpolar oxide interface greatly expands the class of materials whose behavior can be patterned and reconfigured at extreme nanoscale dimensions.     

Luminescence of Eu3+ and Pr3+ in the weberite,Ca2La3Sb3O14

The spectroscopic properties of the Eu³⁺ and Pr³⁺ ions in the weberite, Ca₂La₃Sb₃O₁₄ are examined in this paper. The Eu³⁺ is used as a structural probe ion to elucidate the local site symmetry of the La³⁺ ion in Ca₂La₃Sb₃O₁₄. The interpretation of the Eu³⁺ emission spectrum is not consistent with the C_2h and S₂ (C_i) point symmetry that are prescribed for the La³⁺ sites by the I2/m11 space group of Ca₂La₃Sb₃O₁₄. The emission spectrum of Ca₂La₃Sb₃O₁₄:Pr³⁺ is dominated by emission transitions emanating from the ¹D₂ state. The low energy of the Pr³⁺4f² → 4f¹5d¹ interconfiguration excitation transition in Ca₂La₃Sb₃O₁₄ (3.83 eV or 32 258 cm⁻¹) is attributed to the high covalence which is induced by short Pr³⁺O²⁻ bond distances within the coordination polyhedral units in the lattice. The high covalence of chemical bonding appears to be the hallmark of the weberite structure. A study that compares the optical properties of Eu³⁺ and Pr³⁺ in the weberites, Ca₂La₃Sb₃O₁₄ and NaGdSb₂O₇ is presented.     

Stabilization of the perovskite phase and dielectric properties in the Pb(Mg1/3Nb2/3)O3—BaTiO3 system

The stability of the perovskite phase of PMN ceramics was investigated as a function of BaTi0₃ content and the dielectric properties of various compositions in the PMN-BaTi03 system are presented.The pyrochlore phase in PMN was completely eliminated by the addition of 4 to 5 m/o BaTi0₃. The dielectric constant increased slightly with BaTi0₃ up to the composition in which the pyrochlore phase was eliminated but decreased with further addition of BaTi0₃. The addition of BaTi0₃ lowered the transition temperature and decreased the lattice constant. PMN-BaTi0₃-PbTi0₃ compositions useful for capacitors are identified.     

Variation of the photoluminescence and vacuum ultraviolet excitation characteristics of BaZr(BO3)2:Eu3+ by the incorporation of Al3+, La3+, or Y3+ into the lattice

The photoluminescence (PL) and vacuum ultraviolet (VUV) excitation properties are studied for the BaZr(BO₃)₂:Eu³⁺ phosphor with incorporating the Al³⁺, La³⁺, or Y³⁺ ion into the lattice. The excitation spectrum shows an absorption band in the VUV region with the band-edge at 200 nm and a very weak charge transfer band of Eu³⁺ at about 226 nm. The luminescence spectrum shows a strong emission at 615 nm (⁵D₀ → ⁷F₂ transition) and weak emission at 594 nm (⁵D₀ → ⁷F₁ transition) in BaZr(BO₃)₂:Eu³⁺, with a good red color purity. The PL intensity is increased by incorporating Al³⁺ into the BaZr(BO₃)₂ lattice. The PL intensity has also increased by incorporating La³⁺ into the lattice, however, the red color purity has deteriorated because of the increased centrosymmetric nature of the site. With the incorporation of Y³⁺ into the BaZr(BO₃)₂ lattice, the PL characteristics of the Eu³⁺ activator resembles that in the YBO₃ lattices. The intensity of the red PL for the Eu³⁺ activator is the highest with good color purity for BaZr(BO₃)₂:Eu³⁺ incorporated with both Al³⁺ (10%) and La³⁺ (0.5%).