Papers by Author: G. Branković

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Authors: M. Žunić, Z. Branković, G. Branković, D. Poleti
Abstract: The effect of Co, Cr and Nb on the electrical properties of the grain boundaries of SnO2-based varistors was investigated. The powders were prepared by the method of evaporation and decomposition of solutions and suspensions. Varistor samples were obtained by uniaxial pressing followed by sintering at 1300 °C for 1h. The electrical properties of the grain-boundary region, such as resistance (R) and capacitance (C), were determined using ac impedance spectroscopy in the 27-330 °C temperature interval. Activation energies for conduction (EA) were calculated from the Arrhenius equation. The non-linear coefficients (α) and the breakdown electric fields (Eb) of the samples were determined from the current-voltage characteristics. The potential barrier height (Φb) was calculated using the Schottky-type conducting model. After a comparison of the characteristic parameters for different varistor compositions it was found that the Cr/Nb ratio has a crucial influence on the grain-boundary properties in SnO2 varistors.
Authors: Z. Branković, G. Branković, K. Vojisavljević, M. Počuča, Tatjana Srećković, Dana Vasiljević-Radović
Abstract: The modified polymeric precursor method (Pechini method) was successfully used for the preparation of epitaxial and polycrystalline ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films. Films were deposited on LaNiO3 (LNO) – coated silicium (1 0 0) and platinum substrates (Pt (1 1 1)/Ti/SiO2/Si) by spin coating technique. LNO electrodes were also prepared by the Pechini method and treated under different thermal treatment conditions to obtain films with different structural and microstructural properties. Investigation of PZT microstructure was performed as a function of orientation and morphology of the bottom electrode, as well as of thermal treatment conditions. Grain size and morphology were analyzed by AFM, while the quality and orientation of PZT films were determined by GIXRD analysis. It has been found that the proposed thermal treatment on a hot plate, with slow heating rate and long annealing time, can result in the formation of epitaxial PZT films on Si and LNO-coated Si substrates.
Authors: Katarina Djuriš, G. Branković, Z. Branković, Slavko Bernik, M. Počuča, D. Poleti, B. Antić
Abstract: In this work pure and doped LMO were prepared using modified Pechini method from lanthanum and manganese citrates. Lanthanum citrate was prepared starting from La2O3, while manganese citrate was prepared from Mn(NO3)2. Valence state of the manganese was controlled by adjusting pH value of the solution and confirmed by EPR and UV/VIS analysis. Thermal treatment conditions for preparation of LMO powders were determined from TG/DTA of dried precursors. XRD results confirmed that pure perovskite phase was successfully prepared in single LMO and Cadoped LMO. SEM and measurements of specific surface area of the powders showed the existence of large agglomerates consisting of submicronic primary particles.
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