Phase transitions in gallium nanodroplets detected by dielectric spectroscopy |
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Authors: | G B Parravicini A Stella M C Ungureanu P G Merli A Migliori P Cheyssac and R Kofman |
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Institution: | (1) INFM, Dipartimento di Fisica A. Volta, Università di Pavia, Via Bassi 6, 27100 Pavia, Italy;(2) Saint-Gobin Recherche, 39 quai Lucien Lefranc, 135, 93303 Aubervilliers Cedex, France;(3) LAMEL, 40129 Bologna, Italy;(4) LPMC, Université de Nice Sophia Antipolis, 06108 Nice Cedex 2, France;(5) Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, 56126 Pisa, Italy |
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Abstract: | Both theoretical and experimental works give evidence that
gallium exhibits solid phases labelled , , , besides the
stable phase strongly dependent both on the size and the
confinement conditions. An experimental technique was used based
on capacitance and conductance measurements
vs. temperature in the
audiofrequency range. This technique is particularly sensitive
to the conditions of the investigated particle surface that
plays a fundamental role in the melting and more generally in
the phase transition processes. In particular the strict
relation between the derivative of the capacitance with respect
to the temperature, dC/dT, and the entropy of the system is
considered. In gallium nanoparticles 20 nm in radius, only the
phase is shown to occur. Further the transition to liquid phase
was detected. The melting process was found to start about 65 K
below the full melting temperature value. In the case of
particles 10 nm in radius, where different metastable phases may
occur, the capacitance vs.
temperature curve was found to display abrupt changes of the
slope. The singularities are associated to a well defined
transition temperature. |
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Keywords: | 65 80 +n Thermal properties of small particles nanocrystals nanotubes 64 70 Nd Structural transitions in
nanoscale materials 77 22 Ej Polarization and depolarization 67 57 Np Behavior near interfaces |
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