Microwave properties of HTS films: measurements in millimeter wave range

A theoretical and experimental justification of an approach proposed and developed by us for surface impedance standard measurements of HTS films is presented. An analysis of the electromagnetic properties of quasi-optical dielectric resonators with conducting endplates, which provides a theoretical background for studies of HTS films in the millimeter wave range, is performed. With this technique, the highest quality modes, namely whispering gallery modes, are excited in a dielectric cylindrical disc sandwiched between HTS films. Considerable enhancement of the sensitivity of surface resistance measurements in the millimeter wave range is demonstrated, which is important for the fundamental investigation of superconductor physics. It is also shown that the measured frequency shift in the resonator with the HTS endplates as a function of the temperature reveals a possibility for accurate evaluation of the field penetration depth in HTS films

Thermionic properties of lutetium borides single crystals

Results of the LuB₁₂ (100), (110), (111), LuB₄ (001), LuB₂ (001) thermionic properties study in the temperature range T = 1200...1960 K at p ≤ 10⁻⁴ Pa pressure are presented. The correlation between structure and composition of the lutetium borides single-crystal samples and their thermionic properties are shown. The electron work function anisotropy of the LuB₁₂ low-index planes are determined by the lutetium and boron atoms reticular density and the electric dipole moment of the unreconstructed (100), (110), (111) planes of the UB₁₂ type lattice structure

Thermionic properties of LaB₆-(Ti₀¸₆Zr₀¸₄)B₂ material

The thermionic emmision peculiarities of filber reinforced boride composite ceramic material LaB₆-(Ti₀¸₆Zr₀¸₄)B₂ produced by directional crystallization of eutectic alloy have been studied. Activation modes, electron work function temperature dependence, poisonin under air leakink have been determined. The obtained data are compared with emission characteristics of (100) LaB₆ single crystal and quasi-binary eutectic materials LaB₆-TiB₂ and LaB₆-ZrB₂

Study of the crystalline electric field in PrxLa1-xAl3

Nous avons réalisé des expériences de diffraction inélastiques de neutrons sur des échantillons polycristallins de PrxLa1-xAl3 (x = 1,0 ; 0,75 ; 0,50 ; 0,25) dans le but d'étudier la corrélation entre le champ cristallin (CEF) et les caractéristiques du comportement des électrons de conduction dans les intermétalliques de terres rares. Nous faisons une analyse qualitative des relations observées en tenant compte de l'effet de la variation du paramètre de réseau sur la base du modèle de charges ponctuelles, de la présence possible de distorsions locales de symttrie et d'un certain nombre de mécanismes de relaxation.Inelastic neutron scattering experiments were performed on PrxLa1-xAl3 polycrystalline specimens (x = 1.0 ; 0.75 ; 0.50 ; 0.25). Relationships of energetic positions and widths of a number of peaks in neutron scattering spectra with Pr concentration were obtained. A qualitative analysis of observed relationships is made by taking into account the effect of the lattice parameter variation on the basis of the effective point charges (EPC) model, the possible presence of local distortions of symmetry and a number of relaxation mechanisms