الفهرس 
Features of Amorphous StateOnly 14 pages are availabe for public view
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Abstract
Chalcogenide glasses with chemical formula InxTe20−xSe80 (x = 5, 10
and 15 at %) and SbyTe20−ySe80 (y = 5, 10 and 15 at %) were prepared using
melt quenching method. X-ray diffraction analysis showed that all samples
contain crystalline phases. Detected phases were generally identified as
trigonal In2Se3 and trigonal Se for In-system and orthorhombic Sb2Se3,
trigonal Sb2Te3 and trigonal Se for Sb-system.
Thermal behavior of prepared samples was investigated by using
differential scanning calorimetry at different heating rates, 5, 10, 15 and 20
°C/min. Investigation asserted that all samples contain amorphous phases.
All scans exhibited three well known transitions of chalcogenides, glass,
crystallization and melting. Homogeneity of amorphous phases was
reflected by appearing single glass and crystallization transition peaks.
Obtained values of transition temperatures of all samples shifted generally
to higher values as heating rate increased.
Lasocka relation was used to study heating rate dependence of glass
and crystallization temperatures. Glass and crystallization temperatures and
Lasocka parameters decreased with increasing compositions x and y. It was
observed that glass temperature Tg and crystallization temperature Tc values
of In-system samples are lower than those of Sb-system samples.
Kissinger and Mahadevan models were used to determine glass and
crystallization activation energies. Results obtained from both models were
close to each other. Glass activation energy increased with increasing
compositions x and y, while crystallization activation energy decreased in
general. It was found that glass activation energy Eg and crystallization
activation energy Ec values of In-system samples are generally higher than
those of Sb-system samples.
Isothermal crystallization was studied by measuring time dependence
of ac conductivity at 1 kHz at different annealing temperatures, 75, 80, 85
and 90 °C. All runs manifested well known sigmoidal shape curves of
amorphous materials. Avrami exponent n and rate constant K were
determined by applying JMA equation. Avrami exponent values obtained
revealed that crystallization process in studied samples occurs through
contribution of different mechanisms suggesting that dominant process may
be surface nucleation with one dimensional growth.
Crystallization activation energy Ec and frequency factor K0 were
determined from temperature dependence of rate constant K using
Arrhenius relation. Values of crystallization activation energy Ec obtained
agreed with those determined from non-isothermal methods. Frequency
factor K0 decreased with increasing concentrations of In and Sb. It was
found that lnK0 values of In-system samples are higher than those of Sbsystem
samples.
AC conductivity σ, dielectric constant κ and loss tangent tanδ were
measured using two probe method in frequency range from 100 Hz to 5
MHz and temperature range from 26 to 100 °C. All graphs exhibited usual
dispersion and temperature variation of chalcogenide glasses. Conduction
activation energy E was determined from temperature dependence of
conductivity using Arrhenius relation. Conductivity, dielectric constant and
loss tangent decreased with increasing In-content and increased with
increasing Sb-content, but activation energy decreased with increasing
both. It was found that E values of In-samples are lower than those of Sbsamples,
while σ, κ and tanδ values are generally higher.