Synthesis and Growth of New Compounds Au3In5Se9 and Au3Ga5Se9

The phase analysis was performed and a character of interaction in AuInSe₂ - In₂Se₃ and AuGaSe₂ -Ga₂Se₃ quasi-binary systems were considered. The technology of synthesis and growth of single crystals of new semiconducting compounds Au₃In₅Se₉ and Au₃Ga₅Se₉ were developed. The materials for ohmic contacts were chosen and the electrical, optical and thermal properties of obtained compounds have been investigated. The forbidden band gap, its temperature coefficient, the type of the optical transitions and heat capacity of Au₃In₅Se₉ and Au₃Ga₅Se₉ compounds were determined. The charge of entropy and enthalpy has been estimated by numerical integration.     

The magnetic properties of some R5Pt3 compounds (R = Gd, Tb, Dy, Ho)

The magnetic susceptibility and magnetization of the R₅Pt₃ intermetallic compounds have been studied. Gd₅Pt₃ is ferromagnetic while Tb₅Pt₃, Dy₅Pt₃ and Ho₅Pt₃ possess rather a non-linear magnetic structure, with strong ferromagnetic interaction and high anisotropy effects at low temperatures.     

Raman scattering in low stage compounds of graphite intercalated with AsF5, HNO3 and SbCl5

Raman measurements on low stage compounds of graphite intercalated with AsF₅, HNO₃ and SbCl₅ are reported. The spectrum of the stage 1 C₈AsF₅ acceptor compound is found to be in sharp contrast with that reported for the donor stage 1 C₈M(M=K, Rb, Cs) compounds. Whereas the stage 1 donor compounds have been found to exhibit a characteristic broad, asymmetric Breit-Wigner line shape, the spectrum of C₈AsF₅ contains a single Lorentzian line in this frequency region. Temperature studies of the bounding layer mode lineshape parameters in C₈AsF₅ showed no evidence of the order-disorder transition in the adjacent intercalate layer. The bounding layer mode frequencies of AsF₅, HNO₃ and SbCl₅ graphite are reported, but no intercalate layer modes were observed.     

Metastable complex defects in α-(Al0.02In0.98)2Se3

The electrical properties of α-(Al_0.02In_0.98)₂Se₃ were investigated. In contrast to In₂Se₃, which is characterized by a high and constant concentration of donorlike defect centers, the concentration of active donors in α-(Al_0.02In_0.98)₂Se₃ can be changed in a reversible manner over four orders of magnitude by thermal treatment. To explain this strange behavior, we have proposed a simple model, which presumes formation of complex defect centers consisting of Al atoms at cation sites and native donors.     

Magnetic properties of the hexagonal NdNi5 and NdCu5 compounds

Magnetization and resistivity measurements performed on the hexagonal NdNi₅ and NdCu₅ compounds are presented. For NdNi₅, magnetization was measured on a single crystal along the three main axes of the orthohexagonal cell. This compound orders ferromagnetically at T_c = 7 K, a being the easy magnetization axis. Quantitative analysis of the experimental data led to the determination of the 4f-Nd and 3d-Ni contributions to the magnetization. In particular crystal field parameters were determined which account for inelastic neutron scattering data. Two original features of the compounds magnetic behaviour due to crystal field effects are noted: i) in the basal plane a large anisotropy of the magnetic moment which strongly increases with the magnetic field between 11 and 130 kOe; ii) a large decrease of the Nd moment during the rotation toward the c axis driven by the field. NdCu₅ orders also ferromagnetically at 15 K. The Nd moment lies perpendicular to c, and its reduction by the crystal field seems smaller than in NdNi₅.     

Temperature dependence of the Urbach energy in ordered defect compounds Cu-III3-VI5 and Cu-III5-VI8

Two previous models used with success in Cu-III-VI₂ semiconductors have been employed to study the temperature dependence of the Urbach energy in ordered compounds Cu-III₃-VI₅ and Cu-III₅-VI₈. The model which contains two variable parameters seems to explain better the data over the whole temperature range studied. However, the ordered vacancy or the donor acceptor defect pair in the cation sublattice provides new features in these compounds that need further study.     

Resistivities of CeAl3 and LaAl3 compounds under pressure

The electrical resistivity of CeAl₃ and LaAl₃ compounds has been measured in the 1.3 – 300K temperature range and under pressure up to 17 kbar. The pressure dependence of the resistivity above 25K is theoretically explained by the influence of the crystalline field on the Kondo effect, while the variation of the resistivity at low temperatures or with pressure cycles is qualitatively discussed.     

The electrical conductivity of δ-Bi2O3 stabilized by isovalent rare-earth oxides R2O3

The phenomenon of δ-phase stabilization in the systems (Bi₂O₃)_0.75(R₂O₃)_0.25 where R = lanthanide metal (including La, but Pm excepted) was investigated. The electrical conductivity of those systems, which did show δ-stabilization, was investigated; the system (Bi₂O₃)_1−x(Yb₂O₃)_x was studied in more detail. A Vegard-like relation between the cubic cell-axis and cationic radius of the substituted trivalent metal ion was found. A model is presented which accounts for results of electrical conductivity measurements and thermogalvanic measurements as well.     

PMR spin lattice relaxation by reorientational motions of NH3 and CH3 groups in some organic compounds

The spin-lattice relaxation times, T₁, of protons in o, m, p-phenylene-diamine dihydrochlorides C₆H₄(NH₂)₂·2HCl, phenylhydrazinium chloride C₆H₅NHNH₃Cl, hexaethylbenzene C₆(CH₂CH₃)₆, tetrabutylammonium bromide [CH₃(CH₂)₃]₄NBr, iodide [CH₃(CH₂)₃]₄NI, tetraheptylammonium bromide [CH₃(CH₂)₆]₄NBr and iodide [CH₃(CH₂)₆]₄NI powders have been measured between 400 and 100 K at 60MHz. The experimental results have been explained by considering the reorientational motions of ?NH₃⁺ and ?CH₃ groups about C₃ axes and their role of behaving as sinks to rapid spin diffusion of the ring protons of the phenylene and the methylene protons. The observed T₁, minima in all these substances turn out to be the measures of the ratios between the total number of protons and the number of reorienting ?NH₃⁺ or ?CH₃ protons. Therefore it has been concluded that the T₁, minima of ?NH₃⁺ and ?CH₃ groups, when obtainable can indicate their number present in a solid sample.     

Diode laser heterodyne measurements on 14NH3

The frequencies of 32 absorption lines of ¹⁴NH₃ were measured to within 2 × 10^?4 cm^?1 in the 9- and 10-μm regions by use of a diode laser heterodyne spectrometer.     

High electronic specific heat of some cubic UX3 intermetallic compounds

The low temperature specific heat of cubic UX₃ intermetallic compounds with X = Al, Ga, In, Si, Ge and Sn have been measured. High values for the coefficient of the electronic specific heat have been found, ranging from 14 to 169 mJ/mol K².     

Oxygen adsorption on the surface of In2O3 and β-(Ga0.8In0.2)2O3 mixed oxides porous structure

The paper is devoted to the oxygen sensing properties of In_1.2Ga_0.8Se₃ own oxide. The results are compared with theoretical adsorption kinetics. Temperature and time dependences of adsorption mechanisms are discussed.     

Phase formation and characterization of Sr3Y2Ge3O12, Sr3In2Ge3O12, and Ca3Ga2Ge3O12 doped by trivalent europium

This work reports on the phase formation during a solid-state reaction of Eu³⁺-doped garnets with the general formula A₃B₂Ge₃O₁₂ (A=Ca, Sr and B=Ga, In, Y) and their luminescent properties. It is shown by XRD and DTA/TG experiments that the garnet-phase formation is completed at 1100-1200 °C. Moreover, it turned out that the position of the oxygen to europium charge-transfer band and the intensity of the forbidden 4f-4f transitions of Eu³⁺ is dependent on the covalent interaction between the Eu³⁺ activator and the surrounding oxygen anions. The investigated red-emitting luminescent materials show high lumen equivalents and deep red emission at the same time, which makes them attractive for the application in LEDs (light emitting diodes), in particular for near UV-emitting LEDs.     

The de Haas-van Alphen effect of graphite intercalation compounds with SbCl5 and HNO3

The de Haas-van Alphen (dHvA) effect of SbCl₅-graphite intercalation compounds of stage 2, 3 and 4, and residual HNO₃-compound of stage 3 has been studied. The dHvA spectra are stage dependent, and no combination frequency relations are found, which are in disagreement with Batallan et al.'s report. The amount of charge transfer per intercalant estimated on the basis of the rigid band model is 0.44, 0.49 and 0.43 for stage 4, 3 and 2 SbCl₅-compounds and is 0.14 for stage 3 HNO₃-compound.     

Piezoreflectance measurements on GaxIn1−x Sb alloys

Piezoreflective experiments between 77 and 300°K are performed on Ga_x, In_1?x Sb alloys. E_o and E_o + Δ_o transition energies, vs composition are determined. Band gap E_o variations, are obtained in good agreement with the two band dielectric model. The Δ_o splitting is observed to be linear with composition.The fundamental edge temperature coefficient β is also determined, it is found to vary linearly with composition.E_o and E_o + Δ_o energy determination permit one to deduce effective mass and g_e value variation with composition.     

Electrical transport measurements in TiS3

Results of measurements of conductivity and Hall coefficient in the temperature range 15–300K and of thermal emf in the temperature range 80–400K, carried out on TiS₃ samples, are reported. The results indicate that these crystals are semiconducting with extrinsic n-type conductivity. The mobility of the carriers is about 30 cm²/V sec at room temperature, increases up to about 100 cm²/V sec at 100K and drops at lower temperatures. The Seebeck coefficient is in qualitative agreement with these findings but its detailed temperature dependence is not yet understood.     

Analysis of low temperature specific heat in Nd0.5Sr0.5MnO3 and R0.5Ca0.5MnO3 (R=Nd,Sm, Dy and Ho) compounds

We report on the specific heat C(T) of doped manganites Nd_0.5Sr_0.5MnO₃, Nd_0.5Ca_0.5MnO₃, Sm_0.5Ca_0.5MnO₃, Dy_0.5Ca_0.5MnO₃ and Ho_0.5Ca_0.5MnO₃ in the temperature range 2?T?300 K using modified rigid ion model (MRIM). The present specific heat results are in general satisfactory agreement with experimental data except at very low temperatures (i.e. T?12 K). Also a sharp peak observed in the experimental results for these compounds around 5 K could not be revealed by our computed results as they arise due to Schottky-like anomaly. Besides, we have reported the cohesive and the thermal properties of these compounds. The results obtained by us are discussed in detail.     

Phase diagrams of CuCl2·2NC5H5 and CsCuCl3

The phase diagrams of two quasi one-dimensional,$\text{S =}\text{1}\text{2}$ quantum systems CuCl₂·2NC₅H₅ and CsCuCl₃, have been determined experimentally for fields between 0 and 90 kOe. The results show an increase of the Néel temperature as a function of the field, in accordance with earlier observations on manganese systems.