Infrared spectroscopy of Bi2Te2Se

The infrared reflection and transmission spectra of Bi₂Te₂Se single crystals grown by the modified Bridgeman method have been studied in the spectral range of 30–10000 cm^?1 at temperatures of 5–300 K. The bandgap and its temperature dependence, optical function spectra, and concentration of free charge carriers in Bi₂Te₂Se have been determined.     

High-temperature heat capacity of Dy2Cu2O5

Data on the heat capacity of Dy₂Cu₂O₅ in the temperature range 346–981 K have been obtained. The experimental data have been used for determining the thermodynamic properties of this oxide compound.     

High-temperature heat capacity of Y2Cu2O5

The temperature dependence of the molar heat capacity of Y₂Cu₂O₅ has been measured at 328–953 K. The thermodynamic functions of the oxide compound have been calculated from the experimental data.     

Plasmonics properties of trimetallic Al@Al2O3@Ag@Au and Al@Al2O3@AuAg nanostructures

Bimetallic and trimetallic nanoparticles have attracted significant attention in recent times due to their enhanced electrochemical and catalytic properties compared to monometallic nanoparticles. The numerical calculations using Mie theory has been carried out for three-layered metal nanoshell dielectric–metal–metal (DMM) system consisting of a particle with a dielectric core (Al@Al₂O₃), a middle metal Ag (Au) layer and an outer metal Au (Ag) shell. The results have been interpreted using plasmon hybridization theory. We have also prepared Al@Al₂O₃@Ag@Au and Al@Al₂O₃@AgAu triple-layered core–shell or alloy nanostructure by two-step laser ablation method and compared with calculated results. The synthesis involves temporal separations of Al, Ag, and Au deposition for step-by-step formation of triple-layered core–shell structure. To form Al@Ag nanoparticles, we ablated silver for 40 min in aluminium nanoparticle colloidal solution. As aluminium oxidizes easily in water to form alumina, the resulting structure is core–shell Al@Al₂O₃. The Al@Al₂O₃ particle acts as a seed for the incoming energetic silver particles for multilayered Al@Al₂O₃@Ag nanoparticles is formed. The silver target was then replaced by gold target and ablation was carried out for different ablation time using different laser energy for generation of Al@Al₂O₃@Ag@Au core–shell or Al@Al₂O₃@AgAu alloy. The formation of core–shell and alloy nanostructure was confirmed by UV–visible spectroscopy. The absorption spectra show shift in plasmon resonance peak of silver to gold in the range 400–520 nm with increasing ablation time suggesting formation of Ag–Au alloy in the presence of alumina particles in the solution.     

Electronic to ionic conductivity of glasses in the Li2S–Sb2S3–P2S5 system

There is great interest in sulfide glasses because of their high lithium ion conductivity. New sulfide glasses in the Li₂S–Sb₂S₃–P₂S₅ system have been synthesized by classical quenching technique. The glass domain relays on the medium-lithium content (up to 50% molar).Electrical conductivities of the samples have been determined by Impedance Spectroscopy. The isothermal conductivity curves exhibit two regions on dependence of lithium content implying that the conductivity mechanisms in these two regions are different. The compositions of low lithium content (below 20% mol.) have presented low electronic conductivities close to 10^− 8 S/cm at room temperature. The compositions of medium lithium content (30–50% mol.) could be mixed ionic–electronic conductors with predominant ionic conductivities with a maximum close to 10^− 6 S/cm for sample with 50% Li₂S at room temperature. Arrhenius exponential behavior is verified between 25 °C and T_g for all glasses. The activation energies, determined from temperature dependence, are 0.55–0.64 eV. A comparative study with glasses belonging to the other chalcogenide systems has been undertaken on base of the weak electrolyte model and the values of decoupling index, R_τ, are reported. The impedance of the 0.5Li₂S–0.3Sb₂S₃–0.2P₂S₅ ionic conductor can be described by an equivalent circuit R(RQ)(RQ).     

Phase transitions of [M(H2O)6](MnO4)2 polycrystalline compounds,where M=Mg2+,Ni2+,Zn2+,Cd2+, studied by DSC

Phase transitions of [M(H₂O)₆](MnO₄)₂, where M=Mg, Ni, Zn and Cd, have been studied at 100–400 K by differential scanning calorimetry (DSC). One solid–solid phase transition for the compounds with M=Mg and Ni and two solid–solid phase transitions for these with M=Zn and Cd have been discovered. Additionally, three phase transitions, connected with three-stage melting process of these compounds, were also found. Thermodynamic parameters of the all detected phase transitions were calculated.     

Reactivity between CuxV2O5 and AgyV2O5 bronzes studied by spark plasma sintering

A method based on the analysis of reaction layers that form in Cu_xV₂O₅–Ag_yV₂O₅ interdiffusion couples annealed by spark plasma sintering to quickly explore the Cu–Ag–V₂O₅ ternary system at high pressure is presented. Through use of microanalysis profiling, the phases occurring in this system have been obtained much faster than by conventional techniques of solid-state chemistry. Microdiffraction profiling has also been used to properly identify the Cu_0.5Ag_0.5V₂O₅ phase in the reaction layer between CuV₂O₅ and Ag_0.8V₂O₅. The stability domains of the phases have been approximately determined and interpreted. In most cases, reaction kinetics occurs quickly, as expected by the high diffusion coefficient of Cu and Ag in V₂O₅. Though the experiments have been carried out under high pressure (75 MPa), the same phases are obtained than with sealed quartz tubes experiments.     

Synthesis and properties of HgI2 intercalation of Bi2Sr2CaCu2Oy superconductor

Polycrystalline or single crystals of HgI₂ intercalated Bi₂Sr₂CaCu₂O_y (Bi2212) have been synthesized and their properties have been studied together with those of HgBr₂ intercalates. Single crystals of HgI₂ intercalated Bi2212 were synthesized by a stepwise intercalation method using iodine intercalate as a secondary host material. These could not be obtained through direct intercalation methods by which polycrystalline sample were obtained. From ac susceptibility and resistivity measurements, superconducting onset temperature (T_con) for polycrystalline HgI₂ intercalate was found to be 82 K which was higher than that of the host (75 K). On the other hand, T_con for single crystal HgI₂ intercalate was shown to be 79–80 K which is lower than that of host (95–97 K). The effect of HgI₂ or HgBr₂ intercalation on T_c tried discussion from the view point of hole doping and interblock coupling effect.     

The stretching–bending bands of 13C2HD

The infrared spectrum of ¹³C₂HD has been investigated using high-resolution Fourier transform infrared spectroscopy. A large number of ro-vibrational transitions in the spectral region 1000–6600?cm^?1 have been recorded and assigned. This paper is focused only on the vibrational bands involving pure stretching, stretching–bending or stretching–stretching modes. In total, 78 bands have been identified and assigned, 29 related to υ₁(CH stretch), 27 to υ₂(CC stretch), and 22 to υ₃(CD stretch). The data pertaining to each stretching mode have been fitted simultaneously in order to obtain accurate sets of rotational and vibrational parameters for the excited states.     

Theoretical and experimental investigations of the properties of Ge2Sb2Te5 and indium-doped Ge2Sb2Te5 phase change material

We have carried out comprehensive computational and experimental study on the face-centered cubic Ge₂Sb₂Te₅ (GST) and indium (In)-doped GST phase change materials. Structural calculations, total density of states and crystal orbital Hamilton population have been calculated using first-principle calculation. 5 at.% doping of In weakens the Ge–Te, Sb–Te and Te–Te bond lengths. In element substitutes Sb to form In–Te-like structure in the GST system. In–Te has a weaker bond strength compared with the Sb–Te bond. However, both GST and doped alloy remain in rock salt structure. It is more favorable to replace Sb with In than with any other atomic position. X-ray diffraction (XRD) analysis has been carried out on thin film of In-doped GST phase change materials. XRD graph reveals that In-doped phase change materials have rock salt structure with the formation of In₂Te₃ crystallites in the material. Temperature dependence of impedance spectra has been calculated for thin films of GST and doped material. Thickness of the as-deposited films is calculated from Swanepoel method. Absorption coefficient (α) has been calculated for amorphous and crystalline thin films of the alloys. The optical gap (indirect band gap) energy of the amorphous and crystalline thin films has also been calculated by the equation \( \alpha h\nu = \beta (h\nu - E_{\text{g }} )^{2} \) . Optical contrast (C) of pure and doped phase change materials have also been calculated. Sufficient optical contrast has been found for pure and doped phase change materials.     

Study of the heat capacity of Lu2Cu2O5 in the temperature range 366–992 K

Experimental data on the molar heat capacity of Lu₂Cu₂O₅ in the temperature range 366–992 K have been obtained. The experimental data have been used to calculate the thermodynamic properties of the oxide compound.     

Observation of a forbidden vibrational absorption band of H2 in nanoporous aerogel

Room-temperature absorption spectra of H₂ in nanoporous aerogel with a pore diameter of ～20 nm have been studied on a Fourier spectrometer in the spectral range of 4000–4800 cm^?1. Absorption at the forbidden transitions of the 0–1 vibrational band has been observed. The recorded spectra of H₂ in aerogel have been compared with the spectra of free high-pressure H₂.     

Polar optic phonons in Hg2Cl2 and Hg2Br2

Far infrared (30–430 cm^?1) reflectivity measurements of Hg₂Cl₂ and Hg₂Br₂ single crystals have been performed in polarized light. The spectra, which are in agreement with group-theoretical predictions, were analyzed by the oscillator fitting procedure and Kramers-Kronig method. The results are compared with the existing data from other measurements and the large anisotropy of polar modes is briefly discussed. The polarization vectors of all long-wavelength symmetry modes were determined group-theoretically.     

Phonon spectrum of lead oxychloride Pb<Subscript>3</Subscript>O<Subscript>2</Subscript>Cl<Subscript>2</Subscript>: Ab initio calculation and experiment

IR and Raman spectra of Pb₃O₂Cl₂ in the range of 50–600 cm^–1 have been detected for the first time. Ab initio calculations of the crystal structure and the phonon spectrum of Pb₃O₂Cl₂ in the framework of LCAO approach have been performed by the Hartree–Fock method and in the framework of the density functional theory with the use of hybrid functionals. The results of calculations have made it possible to interpret the experimental vibration spectra and reveal silent modes, which do not manifest themselves in these spectra but influence the optical properties of the crystal.     

Study of Nd2+ absorption in x-irradiated CaF2, SrF2, BaF2 crystals

The absorption spectra of x-irradiated alkaline-earth fluoride (CaF₂, SrF₂, BaF₂) crystals doped with Nd³⁺ ions have been investigated. X-irradiation results in creating the absorption bands of inter-configuration 4fⁿ–4fⁿ⁻¹–5 d¹ transitions of Nd²⁺. The charge reduction of the neodymium by irradiation is not temperature-stable and the ions reoxidation (Nd²⁺ → Nd³⁺) occurs under heating to 570 K in CaF₂, 520 K in SrF₂ and 470 K in BaF₂.     

Laser induced infrared fluorescence of Cs2 and Rb2

Laser induced cross fluorescence of Cs₂ and Rb₂ molecules in the infrared region (1.0–1.6 μm) has been observed using several exciting wavelengths from an argon-ion laser and a tunable cw dye laser. New emission bands have been observed. The lower states of these bands have gerade symmetry and therefore have heretofore escaped observation by conventional absorption spectroscopy.     

Stark and Frequency Measurements in the FIR Spectrum of H2O2

The submillimeter-wave spectrum of H₂O₂has been recorded by means of a tunable FIR spectrometer. Stark measurements have been performed on three selected transitions in then= 0 state, namely, the 2₂₀–1₁₀(τ = 4 ← 2) at 1 272 297 MHz, the 8₂₆–7₁₆(τ = 1 ← 3) at 882 451 MHz, and the 9₂₈–8₁₈(τ = 1 ← 3) at 962 933 MHz. Accurate values of the transition dipole moments of the molecule have been derived by considering the interaction between the levels involved in the transition and the close near-resonant levels. About 40 new lines, belonging to the^rQ₄and^rQ₅subbranches of the rotational transitions between the lowest torsional states (τ = 1, 2, 3, 4n= 0), have been measured in the 2.8 and 3.4 THz spectral regions and analyzed together with the previously measured millimeter- and submillimeter-wave, as well as IR, transitions.     

An inelastic neutron scattering study of C2H2 adsorbed on type 13X zeolites

The inelastic neutron scattering spectra of C₂H₂ and C₂D₂ adsorbed on a Ag⁺ exchanged 13X zeolite (0–800 cm^?1) and of C₂H₂ on the Na⁺ form (0–300 cm^?1) have been obtained. For the Na-13X system no distinct vibrational modes were observed, however for the Ag-13X systems the low frequency intramolecular modes of the adsorbed gas and some of the vibrations of the adsorbed gas relative to the surface have been assigned. From the deuteration shifts it appears that C₂H₂ and C₂D₂, adsorbed on Ag-13X, are non-linear.     

The absorption cross sections of N2, O2, CO,NO, CO2, N2O,CH4, C2H4, C2H6 and C4H10 from 180 to 700Å

The absorption cross sections of N₂, O₂, CO, NO, CO₂, N₂O, CH₄, C₂H₄, C₂H₆, C₄H₁₀ have been measured photoelectrically in the 180–700 Å region using synchrotron radiation. The absorption cross sections in the region λ ≥ 500 Å was found to be structureless and to increase monotonically with wavelength for all gases. The positions of the structure observed in the 520–720 Å region for N₂, O₂, CO₂ and N₂O are consistent with the various Rydberg series reported by previous authors.     

<Superscript>53</Superscript>Cr NMR study of CuCrO<Subscript>2</Subscript> multiferroic

The magnetically ordered phase of the CuCrO₂ single crystal has been studied by the nuclear magnetic resonance (NMR) method on ⁵³Cr nuclei in the absence of an external magnetic field. The ⁵³Cr NMR spectrum is observed in the frequency range ν_res = 61–66 MHz. The shape of the spectrum depends on the delay tdel between pulses in the pulse sequence τ_π/2–t _del–τ_π–t _del–echo. The spin–spin and spin–lattice relaxation times have been measured. Components of the electric field gradient, hyperfine fields, and the magnetic moment on chromium atoms have been estimated.