2. Articole

Permanent URI for this collectionhttps://msuir.usm.md/handle/123456789/47

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    OBTAINING OF II-VI COMPOUND SUBSTRATES WITH CONTROLLED ELECTRICAL PARAMETERS AND PROSPECTS OF THEIR APPLICATION FOR NANOPOROUS STRUCTURES
    (John Wiley & Sons, 2014) Colibaba, Gleb; Goncearenco, Evghenii; Nedeoglo, Dmitrii; Nedeoglo, Natalia; Monaico, Eduard; Tiginyanu, Ion
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    INFRARED PHOTOLUMINESCENCE OF ZnSe:GD CRYSTALS
    (Elsevier, 2015) Colibaba, Gleb; Goncearenco, Evghenii; Nedeoglo, Dmitrii; Nedeoglo, Natalia
    Photoluminescent and optical properties of ZnSe crystals doped with Gd impurity are investigated in infrared (IR) spectral range. The influence of crystal growth temperature, impurity concentration, stoichiometric deviation and post-annealing cooling rate, concentration of Cr and Cu background impurities, temperature and excitation level on photoluminescent and optical properties of the samples is studied. Based on these investigations, the structure of complex IR photoluminescence (PL) bands is analyzed. Correlation between the component parts of the bands at 1 and 2 µm is found and possibility to control the IR PL spectra by enrichment of the samples with Zn or Se is discussed. Coincidence of the IR PL spectra structure is shown for the samples doped with Gd, Yb, and Cr impurities. The model that explains the formation of complexes based on rare-earth elements (REEs) and Cr and Cu background impurities fixed in the nodes of crystal lattice with tetrahedral symmetry, responsible for IR PL bands, is proposed.
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    THERMAL AND DIELECTRIC STUDIES OF 2,2’-DIHYDROXYBENZOPHENONE
    (Akadémiai Kiadó, 2005) Tomitaka, S.; Mizukami, M.; Paladi, Florentin; Oguni, M.
    Thermal and dielectric properties of 2,2’-dihydroxybenzophenone were studied in relation with the potential progress of crystal nucleation and growth below the ordinary glass transition temperature, Tgα. Differential scanning calorimetry was carried out in a range 100-350 K. The α glass transition was found to occur at Tgα=239 K. Crystallization and fusion were observed to take place when the sample was cooled down to 103 K, but not observed when cooled to 203 K. Crystal nucleation was interpreted as having happened during annealing for a short time at 103 K which is much below the Tgα. Heat capacities were measured in a range 7-350 K by an intermittent heating method with an adiabatic calorimeter. The temperature, enthalpy and entropy of fusion were determined to be 334.46 K, 20.07 kJ mol-1 and 60.01 J K-1mol-1, respectively. Crystal growth was found to proceed even at 220 K below the Tgα, but no glass transition was detected below 220 K. Dielectric losses were measured in a temperature range of 100-250 K and a frequency range of 30Hz-10 kHz. β-Relaxation process was found dielectrically with the activation energy of 22.6 kJ mol-1, and the corresponding glass transition was expected to occur at 76.9 K. It is discussed, based on the “structurally ordered clusters aggregation” model for supercooled liquids and glasses, that the β process is potentially attributed to the crystal nucleation progressing at 103 K.