Elastic properties of ferroelastic LiKSO4 in the temperature range from 20 K to 150 K

Bromberek, Marek (2001) Elastic properties of ferroelastic LiKSO4 in the temperature range from 20 K to 150 K. Masters thesis, Memorial University of Newfoundland.

[img] [English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.

Download (15Mb)
  • [img] [English] PDF - Accepted Version
    Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
    (Original Version)

Abstract

Brillouin spectroscopy was used to investigate elastic properties of ferroelastic lithium- potassium sulfate (LiKSO₄) single crystal in the temperature range from 20 K to 150 K. Particular attention has been paid to the temperature region where structural phase transformations have been reported to occur. -- Samples used in the experiment were prepared from untwinned parts of large single crystals and were not treated thermally prior to the experiments. Due to cracking of samples at approximately 50 K, only the temperature dependence of longitudinal modes is reported. -- The longitudinal mode propagating in the [100] direction was temperature independent over the whole temperature range. The modes propagating in [101] and [011] directions show small anomalies below 50 K. Nothing can be concluded about the nature of the changes or the possible phase transition temperatures from these data. However, the mode propagating along the [001] direction shows a local minimum at 52 K which is associated with a structural phase transition. Cracking of most of the samples used in this work at this tempearture suggests the phase transition to be of the first order. Moreover, a small anomaly of the sound wave velocity propagating in this direction occurs at 38 K. Also a pronaunced increase of Brillouin shift occurred below 28 K. These anomalies disappeared after performing the measurements for the second time on the same sample. This behavior can be attributed to the coexistence of different phases over the whole temperature range, or the influence of phase transitions on the spatial distribution of defects and related local internal stresses. -- The temperature of the ferroelastic phase transition reported earlier in the literature was confirmed to be 185 K. The changes of elastic properties at this temperature are in good agreement with previously reported results. -- Suggestions for further work are included.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/1311
Item ID: 1311
Additional Information: Bibliography: leaves 63-70.
Department(s): Science, Faculty of > Physics and Physical Oceanography
Date: 2001
Date Type: Submission
Library of Congress Subject Heading: Ferroelastic crystals; Phase transformations (Statistical physics); Elasticity

Actions (login required)

View Item View Item

Downloads

Downloads per month over the past year

View more statistics