Materials Literature
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It has been shown that the optical and electrical properties of Sr 0.95 ± x Eu 0.05 Al 2 O 4 ± x depend on composition. A composition with excess alumina was found to have the highest CR efficiency, photoconductivity, and a long‐lasting persistence. A mechanism is proposed which assigns the delayed luminescence to a p…
I The Structure and Physicochemical Properties of Carbides.- Structures.- Thermodynamic and thermophysical properties.- Electrophysical and magnetic properties.- Physicomechanical properties.- Chemical properties.- II Methods of Producing Carbides.- III Carbides of Metals of Group I.- Carbides of the alkali metals.- C…
Salts of the anions LnIIIW10O357–(Ln = La, Ce, Pr, Nd, Sm, Ho, Er, Yb, and Y) and CeIVW10O356– have been prepared and analysed. The formulae of the previously reported 8-tungstocerates are revised. All the anions are unstable outside the pH range 5·5–8·5, and stable solutions of the free acids cannot be obtained. Lant…
The empirical dielectric decay function ϕ(t)= exp –(t/τ0)β, 0< β⩽1 has been transformed analytically and numerically into the frequency dependent complex dielectric permittivity. It is shown that empirical curves give a very satisfactory representation of the dielectric α relaxations observed in polyethyl acrylate, po…
The nature of the electrical conduction process in amorphous solids, using as a basis the ionization of local defects by an applied field, is investigated. It is shown that the Poole-Frenkel effect is a limiting case of a more general analysis that can be extended to cover the experimentally available range of field s…
Hydroxyl groups on the surface of metal oxides are amphoteric in character. From experiments with anatase, rutile, η-alumina, α-Fe2O3,CeO2, and SnO2, half the OH groups are acidic in character, the other half are mainly basic and may be exchanged for other anions. This behaviour is explained by the structure of the hy…
An electromagnetic wave absorber utilizing ferrite or rubber ferrite composed of ferrite powder and rubber is described. In our investigation, the existence of a matching frequency f/sub m/ and a matching thickness t/sub m/ has been found. The terms f/sub m/ and t/sub m/ mean that the ferrite which is backed with a co…
Transparent ferroelectric ceramic materials suitable for a variety of electrooptic applications were found in the quaternary (Pb,La)(Zr,Ti)O 3 system. These PLZT materials are prepared from mixed oxides and hot‐pressed typically at 1100°C for 16 h at 2000 psi. Modifying the lead zirconate‐titanate system with lanthana…
Abstract We propose an equation, based on “reciprocal” mean and force additivity, for calculating the interfacial tension between polymers or between a polymer and an ordinary liquid: where γ 12 is the interfacial tension; γ i the surface tension; γ and γ the dispersion and polar components of γ i , respectively. This…
The Science of Large Molecules POLYMERIZATION Step-Reaction (Condensation) Polymerization Radical Chain (Addition) Polymerization Ionic and Coordination Chain (Addition) Polymerization Copolymerization Polymerization Conditions and Polymer Reactions CHARACTERIZATION Polymer Solutions Measurement of Molecular Weight an…
In recent years methods of data analysis for point processes have received some attention, for example, by Cox & Lewis (1966) and Lewis (1964). In particular Bartlett (1963a, b) has introduced methods of analysis based on the point spectrum. Theoretical models are relatively sparse. In this paper the theoretical prope…
Prior small-polaron hopping theories have tacitly assumed that the lattice relaxes rapidly enough after a jump to permit the treating of successive hops as independent. We conclude that the appropriate relaxation time is too long to permit consistent application of these theories to intermediate-mobility materials suc…
Abstract An investigation is made of the stability of the shape of a moving planar interface between the liquid and solid phases in the freezing of a dilute binary alloy. A nonlinear model is used to describe an experimental situation in which solidification is controlled so that the mean position of the interface mov…
YbP${\mathrm{O}}_{4}$ was found to show weak green (497 nm) luminescence when excited by infrared (1 \ensuremath{\mu}m) light. It is concluded, on the basis of measurements of excitation intensity dependence and decay time, that this luminescence is due to the emission of a photon by a pair of excited ${\mathrm{Yb}}^{…
For some ferrites, containing copper and manganese an investigation was made of the influence of the modification of the cation distribution on the Curie point and the anomaly of the temperature variation of the resistivity in this point. The cation distribution was modified by oxygen treatment and was proved by satur…
A detailed neutron diffraction study of Pd2MnSn and Cu2MnIn shows that both have the fully ordered L21 type of Heusler alloy structure and are ferromagnetic with 190 and 575 °K as their respective Curie temperatures. Pd2MnGe shows a preferentially disordered L21 structure with 0.98 Pd + 0.02 Mn on the A- and C-sites a…
A theory of the thermal mechanism of the switching phenomenon is presented which accounts for the essential experimental features reported. The expressions deduced may be used for sandwich and coplanar thin film structures. The theory gives a quantitative basis to decide whether a certain switching behaviour is therma…
Measurements of the IR optical properties of PuO2 were performed by room temperature reflectivity at normal incidence, and absorption. Results of reflection, analysed by Kramers-Kronig and classical dispersion analyses, are fitted into a dynamical theory of fluorite structures. A comparison is established with UO2 and…
The i.r. and laser Raman spectra of pure, crystalline Caro's acid, H 2 SO 5 , were measured for the first time between 4000 and 30 cm −1 . Most of the fundamental vibrations of the molecule could be identified by comparison with those of the H 2 SO 4 , H 2 O 2 and HSO 5 − species. In addition, a dozen or so of lattice…
Vacuum ultraviolet absorption in alkali-nitrites (NaNO 2 and KNO 2 ) and alkali-nitrates (LiNO 3 , NaNO 3 , KNO 3 , RbNO 3 and CsNO 3 ) has been investigated in the region from 5 to 23 eV at room and liquid nitrogen temperatures. Two types of absorption bands are observed for each of these salts with polyatomic anions…