Zlatko Vučić

Zlatko Vučić
Institute of Physics, Zagreb · solid state physics, superionic conductors, single crystal growth

PhD

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36
Publications
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424
Citations

Publications

Publications (36)
Article
The setting processes in the commercial glass ionomer cement (Fuji IX Fast) and resin modified glass ionomer cement (Fuji II LC) were investigated by the dielectric spectroscopy. The changes in the real and imaginary parts of the dielectric permittivity [ε*(ω)] as well as dielectric loss (tan δ) with time for Fuji IX Fast show several distinct regi...
Conference Paper
Full-text available
Objective: One of the most challenging problems regarding composite resins (CR) is their polymerization shrinkage (PS) induced by photo-polymerization. The aim of the study was to develop a new method for a more reliable and accurate measurement of PS of flowable CR (FCR). We implemented the novel sample holder into the interferometry setup, to ena...
Conference Paper
Full-text available
The purpose of this paper is to present the current activities of a research collaborative program between three institutions from Zagreb (School of Dental Medicine, Institute of Physics, and Institute Ruđer Bošković). Within the scope of this program, it is planned to investigate and find guidelines for the refinement of the properties of dental b...
Article
A decade ago, a burst-like growth mode of c-facets of 4He crystals growing at mK temperatures, characterized by the alternation of time intervals during which the facet does not advance with the intervals of its fast advancement, was found [J.P. Ruutu, P.J. Hakonen, A.V. Babkin, A.Y. Parshin, J.S. Penttilä, J.P. Saramäki, G. Tvalashvili, Phys. Rev....
Article
The growth of spherical copper selenide single crystals (fed by Cu atoms at constant rate) is driven by the gradient of the chemical potential, which is in the absence of facets isotropic and proportional to inverse square of crystal radius. We investigate the influence of the facets on the local chemical potential gradient on the facet site by a m...
Article
In order to measure the radial displacements of facets on surface of a growing spherical Cu_{2-\delta}Se crystal with sub-nanometer resolution, we have investigated the reliability and accuracy of standard method of Fourier analysis of fringes obtained applying digital laser interferometry method. Guided by the realistic experimental parameters (de...
Article
Full-text available
We investigate the reliability of phase retrieval by use of the fringe Fourier analysis method for measuring the displacements of facets during the growth of equilibriumlike-shaped crystals. The mean phase change between two successive interferometric images contains an inherent error that emerges from the noninteger number of fringes in the image...
Article
The motivation behind this work is the discrepancy between the measured and calculated growth rates of copper selenide spherical single crystals between 740 and 800 K. The growth of cylindrical polycrystalline samples of copper selenide at high temperatures was monitored in experiments that enabled full control of the geometry of growth. Together w...
Article
Full-text available
A refined Fourier-transform method of analysis of interference patterns is presented. The refinements include a method of automatic background subtraction and a way of treating the problem of heterodyning. The method proves particularly useful for analysis of long sequences of interferograms.
Article
Several millimetres large spherical cuprous selenide single crystals with well developed (1 1 1) facets grown at about 30 K below the roughening temperature (TR≈830 K) and rapidly cooled to room temperature were used to test the universality and value of critical exponent describing the surface profile behaviour near the facet edge. Enlarged photog...
Article
The electronic conductivity ( sigma c) of copper selenide in the composition range from Cu2Se to Cu1.96Se has been investigated in the temperature interval from room temperature to 430K. Two anomalies found in sigma c against T curves are associated with a long-range order-disorder transition of the cation subsystem and a rhombohedral-cubic transfo...
Article
Full-text available
The spherical equilibrium-like shaped single crystals of nonstoichiometric cuprous selenide have been grown using the modifed Ohachi's method at about 30 K below its roughening temperature, TR(111) = 830 K. The growth has been performed under conditions of a constant volume growth rate. During the growth of partly faceted ((111) facets) and partly...
Article
The equilibrium-like-shaped single crystals of nonstoichiometric cuprous selenide were grown in their high-temperature phase from 480 to 530°C using Ohachi's method. The method had been developed for ionic–electronic mixed conductors, involving macroscopic transport of mobile metal atoms through the polycrystalline bulk, due to a fixed chemical pot...
Article
Full-text available
The construction of an apparatus for measuring the thermal expansion of solids, based on the three-terminal capacitor method, in the temperature range between 273 and 620 K is described. The device enables measurements to be made on samples regardless of their shape, size, conductivity or dielectric constant. The operating range can easily be exten...
Article
Modulations and “pairing” of Bi atoms in the Bi2Sr2CaCu2O8+x high-temperature superconductor are simultaneously observed on the high-resolution electron micrographs, viewed along the [101] crystal direction. We analyze the obtained images by laser diffraction and photodensitometric technique applied to the negatives. The “pairing” of Bi atoms is as...
Article
Full-text available
An X-ray study of the quasi-one-dimensional charge density wave (CDW) system (NbS 4) 10I 3 as a function of temperature from room temperature down to 130 K has been performed by taking oscillation and zeroth level Weissenberg photographs. A reversible transformation of the room temperature tetragonal lattice into four symmetrically-related monoclin...
Article
In order to get better insight into the electrical and thermal transport of (NbSe4)10I3 we performed a detailed measurements of the electrical conductivity and thermopower from 350 K down to 5 K as well as structural investigation in the vicinity of the Peierls transition on the samples selected from the same batch. The observed structural changes...
Article
Full-text available
In order to study the structural background of the giant thermal hysteresis observed in the thermopower measurements [1] of the CDW system (NbSe4)10I3, zeroth-order Weissenberg and oscillation photographs were taken at temperatures below Peierls transition. A reversible transformation of the room temperature tetragonal lattice into four symmetrical...
Article
The electromotive force (EMF) of the Cu/solid electrolyte/Cu2−xSe/Pt cell has been measured for compositions from Cu2Se to Cu1.75Se and temperatures from 140 to 240°C. The improved experimental arrangement increased the precision of measurements. The EMF temperature dependence, which is found to be linear and composition-independent, is attributed...
Article
Full-text available
Thermal expansion coefficient β of the Cu2−xSe sample with 1.975 ⩾ 2 − x ⩾ 1.801 is measured in the temperature interval from 300 to 570 K. In the high-temperature phase the data are well fitted by the expression where P1 is weakly and P2 strongly dependent on x. In a simple configurational model the lattice parameter is increased only by those con...
Article
Full-text available
Single crystal X-ray and electron diffraction investigation of stoichiometric cuprous selenide shows that the structure of β-Cu2Se below 413 K is monoclinic with a unit cell of space group Cm·Z = 12, and cell parameters: am = 0.7115 ± 0.0005 nm, bm = 1.234±0.001nm·cm = 0.7119±0.0005 nm, βm = 108.0±0.4°, at temperature. The monoclinic cell is a supe...
Article
A brief review and some remarks on the theory and practice of the four point dc ionic conductivity measurement in a mixed conductor are presented. Measurements were made on Cu2−xSe which has the electronic to ionic conductivity ratio of 2×103–2×105. The transients which appear on the voltage probes when a constant current is sent through the sample...
Article
The push-rod dilatometric investigations of polycrystalline copper selenide between room temperature and 460 K have been performed. The results obtained for the low-temperature phase are in qualitative disagreement with previous X-ray dilatometric results. Using our own structural data we have succeeded to explain this discrepancy in terms of the a...
Article
Single crystals of cuprous selenide exhibit a considerable dilatometric anisotropy in the low-temperature phase. The anomalies in the thermal dilation curves both along the monoclinic (b) axis and within the basal layers are discussed on the basis of the previous structural results. The anisotropy of the low-temperature phase is shown to be induced...
Article
The nature of the phase transition to the superionic phase of cuprous selenide has been investigated by measuring thermal expansion, electron diffraction, and electronic conductivity. The degenerate nature of the transition has been demonstrated by introducing controlled deviations from stoichiometry. The origin of this first-order phase transition...
Article
The paper deals with the question of under what conditions could a liquid-like subsystem in a superionic conductor be prepared in an amorphous or glassy state. An ad hoc identification of cation subsystems† in some silver and copper salts with real liquids and the application of Uhlmann's method of calculation give the critical cooling rates and th...
Article
Differential thermal analysis on a series of non-stoichiometric samples of cuprous selenide Cu2–δSe has been performed. An unusual behaviour, unlike that in other well-known superionic conductors was found, the phase transition of the main rigid lattice, to the phase which characterizes most superionic conductors, takes place at a temperature 30–40...
Article
The magnetic susceptibility of a series of nonstoichiometric samples was measured between room and liquid nitrogen temperature. Below 220 K a transition from diamagnetic to paramagnetic behaviour was observed. According to some structural and NMR considerations this transition may be regarded as a consequence of Jahn-Teller effect.
Article
Liquid Ge is dispersed under argon atmosphere into a cloud of small spheres. With diameters D less than equivalent to 0. 3 mu m are entirely glassy while those with D greater than 0. 3 mu m are partially or entirely crystalline. Under forced convection cooling conditions the critical diameter of D equals 0. 3 mu m implies a critical cooling rate of...
Article
Thermoelectric power (S) measurements have been made on several supersaturated AlMn alloys containing up to 2 at.% Mn in solid solution. The Mn contribution has been obtained from 2 to 440K to an accuracy of +or-5% by making corrections for phonon scattering and phonon drag. The results are compared with data for the more strongly magnetic alloys,...
Article
The impurity resistivity of Al based 3-d transition metal alloys has been investigated at 4.2 and 500 K. While the impurity resistivity at 4.2K plotted as a function of the atomic number of the transition metal shows a single-peaked structure, the resistivity measured at 500 K follows a double peaked curve characteristic of noble metal alloys conta...
Article
The resistivity of AlMn alloys of concentrations up to 5% is found to decrease linearly in temperature above 50 K, while at lower temperatures it follows the same T2 behavior observed at lower concentrations. The linear behavior of rho(T) rules out the possibility that AlMn is a Kondo system with TK~=500 K. Possible explanations in terms of localiz...

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