National Institute Of Materials Physics - Romania

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838 articles found

631. Comparison between PZT thin films deposited on stainless steel and on platinum/silicon substrate

Authors: Stancu, V; Sava, F; Lisca, M; Pintilie, L; Popescu, M

Published: 2008, INTERFACIAL NANOSTRUCTURES IN CERAMICS: A MULTISCALE APPROACH, 94, DOI: 10.1088/1742-6596/94/1/012012

Pb(Zr1-xTix)O-3 (PZT) thin films were prepared by sol-gel method on stainless steel (SS) and on platinum-coated silicon substrate (Pt/Si). The structure revealed by X-ray diffraction shows strong crystallographic orientation: (110) and (100), respectively. The crystallite size shows significant differences: d((00l))((SS))= 27.1 nm, d((h00))((Pt)) = 88 nm. The tetragonal splitting is (Delta c/c)((ss))=3.55 % and (Delta c/c)((pt))=3.32 %. The ferroelectric hysteresis loop in the static mode is characterized by remanentpolarization of 25 mu C/cm(2) and coercive field of 45 kV/cm for SS substrate, while for Pt/Si substrate the values are 10 mu C/cm(2) and 39 kV/cm, respectively. The leakage current is about 3 orders of magnitude lower in the PZT film deposited on SS. The better properties of the PZT deposited on SS are explained by the presence of large single crystal-like crystallites, which make the film closer to epitaxial ones. The results show the potential of growing epitaxial films on low-price substrates such as stainless-steel.

632. ELECTRIC, FERROELECTRIC AND PHOTOELECTRIC PROPERTIES OF Pb(Zr,Ti)O-3-Nb:SrTiO3 JUNCTIONS

Authors: Pintilie, L; Pintilie, I; Vrejoiu, I; Alexe, M

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703406

The electric, ferroelectric and photoelectric properties of Pb(Zr,Ti)O-3-Nb:SrTiO3 (PZT-STON) junctions were investigated on a broad range of temperatures. It was found that the hysteresis loop is strongly asymmetric, due to the asymmetry in the leakage current. The capacitance-voltage characteristic has a butterfly shape although it is also asymmetric because of the different nucleation and compensation conditions at the two interfaces. The junction shows a strong photovoltaic effect in the 200500 run wavelength range as short-circuit currents Of the order of nA for an illuminated surface of 0.018 mm(2). This makes the PZT-STON junctions attractive for UV optoelectronic applications.

633. A Study of the Changes Produced by Sintering on the Shape and Densification of Green Compacted Samples

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Amarande, L; Plavitu, C; Cioangher, M; Trupina, L; Miclea, CT; David, C

Published: 2008, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 11, 107, DOI:

In order to determine the effect of sample shape, compacting pressure and green density gradients on the final shape and density of sintered bodies a study was made on a PZT type powder, pressed within a large range of shapes from long cylinders up to thin discs and at pressures ranging between 40 and 180 MPa. Important shape distorsion were found for both long cylinders and thin discs but surprisingly the final density was not essentially changed even if the green compacted density showed important changes with in the samples. Differences in the shrink age of diameter and thickness brought about by sintering for samples with different shapes were found.

634. Spectroscopic ellipsometry study of amorphous SrxBa1-xNb2O6 thin films obtained by pulsed laser deposition

Authors: Ion, V; Galca, AC; Scarisoreanu, ND; Filipescu, M; Dinescu, M

Published: 2008, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 5, 5, +, DOI: 10.1002/pssc.200777818

Optical properties of amorphous Strontium Barium Niobate (a-SBN) thin film are investigated using spectroscopic ellipsometry. Since the SBN can be applied to optoelectronic devices, the dispersion of refractive index is desirable. The films are obtained by Pulsed Laser Deposition (PLD) onto MgO and Si substrates by targeting a SBN:60 monocrystal: The dielectric function of a-SBN is approximated using a single Tauc-Lorentz oscillator model. Thicknesses of the films and of their rough layer are in agreement with SEM and AFM results. The dispersion of the refractive index is presented in the 1 - 5 eV range.

635. A HIGH PERFORMANCE PZT TYPE MATERIAL USED AS SENSOR FOR AN AUDIO HIGH FREQUENCY PIEZOELECTRIC SIREN

Authors: Miclea, C; Tanasoiu, C; Iuga, A; Spanulescu, I; Miclea, CF; Plavitu, C; Amarande, L; Cioangher, M; Trupina, L; Miclea, CT; Tanasoiu, T

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703364

A high quality PZT type material was designed and produced in order to be used as sensor for a high internsity siren. Two disks from this materials were assembled into a parallel bimorph type transducer with an intermediate metallic plate. This assembly behaves like an acoustic resonator in the high frequency audio range. The fundamental of the flexural mode for a free resonator is taken into account Its frequency dependence on the geometry of the system and on its material properties is computed using the results for a circular plate with clamped edges and an observation on the equivalence between the movement of a particular part of a resonator in a stationary state and the movement of that pari separated from the resonator but with the same border conditions. Acoustical and impedance measurements were made in order to appreciate the influence of the metallic plate on the frequency. In order to increase the acoustic emission a frontal cardboard horn was added to the resonator.

636. Ferroelectric/Antiferroelectric Pb(Zr0.8Ti0.2)O3/PbZrO3 Epitaxial Multilayers: Growth and Thickness-Dependent Properties

Authors: Boldyreva, K; Pintilie, L; Lotnyk, A; Misirlioglu, IB; Alexe, M; Hesse, D

Published: 2008, FERROELECTRICS, 370, 146, DOI: 10.1080/00150190802384492

Epitaxial ferroelectric/antiferroelectric PbZr0.8Ti0.2O3/PbZrO3 multilayers were grown on SrTiO3(100) substrates, covered with a SrRuO3 (100) bottom electrode and a thin tetragonal PbZr0.2Ti0.8O3 buffer layer, using pulsed laser deposition. Polarization-field, switching current-voltage and capacitance-voltage curves show a mixed antiferroelectric-ferroelectric behavior of the multilayers with an individual layer thickness above 10 nm, but below 10 nm the multilayers show only ferroelectric behavior. Obviously the PbZrO3 layers thinner than 10 nm underwent a transition into the ferroelectric state. An X-ray diffraction -2 scan showed a corresponding orthorhombic-to-rhombohedral transition of the PbZrO3 layers. The observations are discussed in terms of a strain effect.

637. High-Q BZT ceramics for microwave applications

Authors: Ioachim, A; Toacsan, MI; Nedelcu, L; Mihut, L

Published: 2008, PROCEEDINGS OF THE 6TH WSEAS INTERNATIONAL CONFERENCE ON APPLIED ELECTROMAGNETICS, WIRELESS AND OPTI, DOI:

Ba(Zn1/3Ta2/3)O-3 (BZT) ceramics were prepared by solid-state reaction and sintered in air at temperatures in the range 1550-1650 degrees C, for 2 hours. In order to improve the microwave and millimeter wave properties, annealing treatment at 1400 degrees C for 10 hours was applied. The long-range order with a 2:1 ratio of Ta and Zn ions on the octahedral positions of the perovskite structure and the vibrational modes were investigated by using XRD and Raman spectroscopy as function of sintering temperature. Presence of small amount of secondary phase, Ba8ZnTa6O24, affects Q factor even in the dense, highly ordered samples. The dielectric parameters were measured in the microwave range by Hakki-Coleman method and were correlated with structural and optical properties. Sintering temperature higher than 1600 degrees C are required for BZT ceramics in order to obtain low microwave loss (Q x f similar to 100 THz).

638. Correlation of Structural and MW-MMW Dielectric Properties with Vibrational Modes in BaX1/3Ta2/3O3 Complex Perovskites

Authors: Toacsan, MI; Ioachim, A; Nedelcu, L; Banciu, MG; Mihut, L; Szilagyi, A

Published: 2008, 2008 33RD INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES, VOLS 1 AND 2, +, DOI:

Ceramic based Ba(Zn1/3Ta2/3)O-3 materials were prepared by solid-state reaction. Studies on microwave dielectric parameters in correlation with structural and Raman investigations were performed. Sintering temperatures higher than 1600 degrees C are required in order to obtain dielectric properties suitable for millimeter wave applications.

639. Radiation characteristics of a novel compact microstrip patch resonator

Authors: Militaru, N; Banciu, MG; Nedelcu, L; Lojewski, G

Published: 2008, ECCSC 08: 4TH EUROPEAN CONFERENCE ON CIRCUITS AND SYSTEMS FOR COMMUNICATIONS, +, DOI: 10.1109/ECCSC.2008.4611680

In this paper a new type of dual-mode compact resonator for mobile communication systems, in the 900 MHz frequency band, is investigated. This compact planar resonator, developed on a 0.635 mm substrate with a 10.8 dielectric constant, has a square shape with an edge of 20.5 mm. For this dual resonator, several methods of modes coupling were considered. The radiation characteristics of this new resonator were investigated.

640. Combinatorial pulsed laser deposition of thin films

Authors: Craciun, V; Craciun, D; Mihailescu, IN; Socol, G; Stefan, N; Miroiu, M; Galca, AC; Bourne, G

Published: 2008, HIGH-POWER LASER ABLATION VII, PTS 1-2, 7005, DOI: 10.1117/12.782589

Pulsed Laser Deposition (PLD) is an ideal technique to be used for combinatorial approaches. By simply changing the deposition targets one can obtain alternating layers with different periodicities both vertically and laterally, along the substrate surface. By changing the laser impact area location and the number of pulses on each target used for ablation, one can grow films with a continuous variation of the chemical composition, which will be a function of the location on the substrate. To illustrate the advantages and versatility of this Combinatorial PLD (C-PLD) technique, several examples of films used in applications where more than one property should be tailored or optimized are presented. Investigations of thermo-chemical stability, chemical bonding and crystalline structure of thin films of mixtures of HfO2 and Al2O3 that are used as high-k dielectric layers in advanced C-MOS transistors is the first example, followed by a study of structural, mechanical, optical and electrical properties of mixtures of indium tin oxide and doped or pure zinc oxide that are used as transparent and conductive layers. The third example is from the deposition of multilayers of ZrC and ZrN with variable thicknesses to obtain hard coatings.