B. Hadžić

The effect of Sn for Ti substitution on the average and local crystal structure of BaTi1−xSnxO3 (0 ≤ x ≤ 0.20)

The effect of Sn for Ti substitution on the crystal structure of a perovskite, barium titanate stannate (BTS), BaTi1−xSnxO3 for x = 0, 0.025, 0.05, 0.07, 0.10, 0.12, 0.15 and 0.20, was investigated. The powders were prepared by the conventional solid-state reaction technique. The structural investigations of the BTS powders were done at room temperature by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected-area electron diffraction (SAED) and Raman spectroscopy analyses. Rietveld refinement of XRD data indicates that gradual replacement of titanium by tin in BaTiO3 provokes a phase transition from tetragonal for 0 ≤ x ≤ 0.07 to cubic for x = 0.12, 0.15 and 0.20. The coexistence of tetragonal (P4mm) and cubic (Pm\overline 3m) crystal phases was established in powder with nominal composition BaTi0.9Sn0.1O3. The crystal phases determined by Rietveld refinement were confirmed by HRTEM and SAED analyses. The crystal structures of the BTS powders at short-range scale were studied by Raman spectroscopy, which shows tetragonal (P4mm) and a small fraction of orthorhombic (Pmm2) crystal phases for all the examined BTS powders, implying a lower local ordering when compared to the average symmetry.

Photoluminescence study of cobalt (III) and copper (II) complexes with the Schiff base of pyridoxal and aminoguanidine

Transition metal complexes with the Schiff base of pyridoxal and aminoguanidine (PLAG) of the formulas [Co(PLAG–2H)(NH3)3]NO3MeOH (complex 1), [Cu(PLAG–H)N3] (complex 2) and [Cu(PLAG)MeOH](NO3)2 (complex 3) were tested using photoluminescence spectroscopy upon 458, 488 and 514.5 nm laser excitation. Using Lorentzian multipeak technic photoluminescence, the peak positions and their intensities were distinguished. The results indicate that the Co(III) complex gives about two to three orders of magnitude higher photoluminescence than other analyzed materials.

Experimental and Theoretical Investigations of Cured and Uncured Disiloxane Bisbenzocyclobutene Thin Films

The main challenge in the large-scale commercial applications of benzocyclobutene (BCB) dielectrics is to perform their curing rapidly and efficiently at low temperatures, and in the same time, to obtain large area, high quality, pinhole free dielectric thin films. For that purpose, we investigated numerous uncured and cured BCB films, approximately 2 µm thick, spin-coated on glass/ITO surface, using optical and AFM microscopy, infrared (IR) and Raman spectroscopy, and complete these results with appropriate Linear Combination of Atomic Orbitals (LCAO) calculations. That way we relate microscopic characteristics of the involved molecules, and macroscopic properties of the cured and uncured polymers, which is important for their practical applications.