First experimental observation and thermodynamic description of elastic softening in a mineral
A. Tröster, W. Schranz and R. Miletich
How to Couple Landau Theory to an Equation of State
Phenomenological Theory (Landautheory, Pseudospinmodels,..) of Phase Transitions in nonmetallic Solids in combination with Experiments
Sound Propagation in crystals near Phase Transitions
Elastic Behaviour in
Orientational Disorder in molecular Crystals (KSCN, C60, C70,...)
Domains and Domainwall Properties
incommensurate Phases, Theory of the Lock-In Transition, Elastic Properties of Incommensurate Crystals
Influence of Defects
(Point Defects, Dislocations, Domains,..) on the Phase Transition Properties of
Mesoscopic Structures near Phase Transitions
High Pressure Physics
The equipment can be used for determining the thermal expansion and the elastic compliances of crystals. The complex compliances can be routinely measured in a frequency range from 10 mHz to 50 Hz and for temperatures between 100 K and 1300 K. In co-operation with Oxford Instruments we have adapted the measurement cell for temperatures down to 6 K. The resolution in the length change of the sample is 30 nm, the force resolution in determining elastic compliances is 1 mN.
The temperature range covered ranges from 100 K to 1000 K with heating and cooling rates between 0.1 K up to l00Kper minute.
The measurement of the specific heat is performed using ac-calorimetry. A thin sample (thickness 100 m - 300 m , diameter about 3 mm) is periodically (0,5Hz - 1,5Hz) heated by a light beam. The temperature change of the sample thus created (+0,01 K) is measured by Lock-In technique using a thin thermocouple (30 m) as a sensor. The whole experiment is automated using a personal computer. The temperature of the sample in the range from 90 K to 600 K is controlled by a commercial temperature controller. The smallest temperature steps in this experiment are 10 mK. The temperature resolution of the experimental setup is + 2.5 mK.
Dielectric constants for frequencies between I kHz and 10 MHz are determined by measuring the admittance of oriented crystal plates with electrodes either evaporated or silver painted (HP4] 92A and HP4191A). At the low frequency end a Stanford Research Systems DSP Lock-In amplifier (SR850) enables measurements down to I mHz. The temperature of the sample chamber is regulated by a commercial temperature controller (EUROTHERM 818) between 80 K and 550 K or by a closed cycle Helium refrigerator between 20 K and 300 K.
The relative temperature change of the birefringence can be measured using the polarising microscope and the Senarmont compensation method. In a temperature range from 3.8 K to 1700 K the absolute value of the birefringence can be measured using a tilting compensator. The birefringence measurements (even within a single domain) can be performed with uniaxial stress or electric field applied. Domain structure studies as a function of temperature and uniaxial stress and phase front studies can also be performed. The change of the orientation of the index ellipsoid can be studied in the temperature range mentioned. The microscope is equipped with photographic and video facilities for documentation.
Laboratory of Complex Systems, University of Picardie, Amiens, France
Institut für Mineralogie und Kristallographie,
Geozentrum, Universität Wien
E. Tillmanns, E. Libowitzky, M. Götzinger, et al.
Intitut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld, Heidelberg, Germany
Institute of Physics, Czech
Academy of Sciences, Prague
J. Petzelt, S. Kamba, J. Hlinka, I. Rychetsky, V. Janovec, et al.
Institute of Nuclear Physics,
K. Parlinski, P. Zielinski, et al.
Jozef Stefan Institute,
R. Blinc, J. Dolinsek, I. Drevensek-Olenik, I. Musevic, et al
Laboratoire de Mineralogie et
Crystallographie, Universite de Langduoc, Montpellier, France.
P. St. Gregoire
Department on Earth Sciences,
University of Cambridge, UK.
E.K.H.Salje, M. Carpenter
Lviv Polytechnic National University, Lviv, Ukraine
Institute for Computer Science, Technical University of Czestochova, Czestochova, Poland
Nationaler Forschungspartner im FWF-Projekt P 29563-N36 „Relaxors“
Projektleiter: Dr. Marco Deluca, Materials Center Leoben Forschung GmbH
Goal: We aim to uncover the relationship
between polar order and chemical order in Ba-based relaxors using a combination
of Raman spectroscopy and atomistic modelling. In particular we're going to
study homovalent and heterovalent systems based on Zr- and Nb-doping.
Methods: Dielectric Spectroscopy, Raman Spectrum Analysis, Raman Spectroscopy, X-Ray Diffraction, Ferroelectrical Properties, Relaxor Ferroelectrics, Ab Initio Methods
FWF-project P 6758 P (1988-1992): Strukturumwandlungen in reinen und gestörten Kristallen
FWF-project P 8285-TEC (1991-1994). Glasbildung und Phasenübergänge/KSCN Familie
BuMiWuF 45.131/4-IV/6a/92 (1990-1994): Phase Transitions in non-metallic systems into inhomogeneous or disordered phases
BuMiWuF GZ 45.113/3-27/90 (1990-1992): Theoretical description of orientationally disordered crystals
BuMiWuF GZ 45.223/2-27b/91(1991-1994): Dipolar and Quadrupolar Glasses
FWF-project P 09793-PHY (1994-1997): From weakly to strongly disordered systems
FWF-project P 10924-PHY (1995-1998): Disorder and Glassbehaviour in Fullerites
FWF-project P 12226-PHY (1997-2000): Mesoscopic Structures near Phase Transitions
ÖAD-WTZ project (1998-2000): Investigation of Phase Transitions in Synthetic Crystals and Minerals
ÖAD-WTZ project 18/00 (2000-2002): Microscopic mechanical properties of Technologically important Materials studied by theory and experiment
ÖAD-WTZ project 14/02 (2002-2004): Elastic and vibrational properties of selected minerals and other important materials
EC-TMR-Network (1998-2001): Interdisciplinary European network for the quantitative analysis of transformation processes in natural minerals
FWF-project P 15016 (2001-2003): New approaches to strain and elasticity near phase transitions
EU-STCU project No 1712 (2002-2004) Acoustooptic devices for control of superpowerful laser radiation
EU-STCU Coordinator of project No. 3222 (2005-2007) Spatial Anisotropy complete 3D-analysis in geometry optimizations of electro-, piezo- and acoustooptical interactions
Universitäres Schwerpunktsprojekt: "Bulk
Nanostructured Materials: Synthesis, Microsctructures and Properties"
Project Manager: Prof. H.P. Karnthaler
Research Proposers: H.P. Karnthaler, M. Zehetbauer, C. Rentenberger, T. Waitz, G. Krexner, W. Schranz, P. Rogl (FWF)
FWF P19284-N20 (1.12.2006-30.11.2009) "Dynamic Elasticity of Complex Materials" P19284-N20 (duration 3 years)
Initiativkolleg I022-N on „Experimental Materials Science-Nanostructured Materials“
EU-STCU project No 4584 (2009-2011) Development of most efficient acoustooptic cell creation methodology for super-high- frequency control of powerful laser radiation
ÖAD-WTZ project Sl 19/2009 (2009-2010): Dynamische Eigenschaften lichtempfindlicher Flüssigkristall-Elastomere
COST project MP0902 (2009-2013) COINAPO “Composites of Inorganic Nanotubes and Polymers”
FWF P23982-N20 (1.11.2011-31.10.2015) "Multiscale properties of disordered ferroics and glasses" P23982-N20
FWF P28672-N36 (1.1.2016-31.12.2018) "Structure and dynamics of interfaces in ferroic materials" P28672-N36
On 30 Mar 2000, 17:21.