ELFT HÍRADÓ

[Imre Attila <imre AT aeki.kfki.hu>]

Tisztelt Kollegák!
Június 14-én (kedd) Prof. Atul Khanna (Department of Physics, Guru Nanak Dev 
University
Amritsar-143005, India) tart előadást, amelynek címe:
"Exploring the mystery of glass: Investigations in borate, silicate and 
tellurite glasses" (az absztrakt lent található).
Az előadásra minden érdeklődőt szeretettel várunk, kezdés 10.00, KFKI AEKI 
Tanácsterem (XIX. épület, földszínt).

Imre Attila


Attila Imre
KFKI Atomic Energy Research Institute
H-1525 Budapest POB 49, Hungary
(1121 Budapest, Konkoly Thege Str. 29-33, Hungary)
Tel.: +36-1-392-2222, ext.1117 or 3366
Fax: +36-1-392-2684



Exploring the mystery of glass: Investigations in borate, silicate and 
tellurite glasses

Atul Khanna
Department of Physics
Guru Nanak Dev University
Amritsar-143005, India

Email: 
ak.ap AT gndu.ac.in

The study of glasses and melts is a challenging problem of condensed 
matter physics[1]. Glasses are metastable solids that can be prepared by 
melt-quenching, neutron and ion irradiation and pressure induced 
amorphization. Some of the older, yet unanswered questions in glass 
physics are the understanding of fundamental conditions for glass 
formation, the relationship of a liquid with its glass, the origin of 
fragility in glass forming liquids, and the low temperature thermal 
properties of glasses which are strikingly different from crystals. Among 
the more recent and surprising discoveries in glasses and liquids that 
awaits proper understanding: is the phenomenon of polyamorphism first 
discovered in amorphous solidified water (ASW) and more recently in 
Y2O3-Al2O3 glasses, molten phosphours, metallic glasses and carbonic acid.
	During the last decade we have prepared and extensively studied 
mechanical, thermal, optical and structural properties of several borate, 
borosilicate, silicate and tellurite glass systems by techniques like DSC, 
infrared, UV-visible, high field MAS-NMR spectroscopy, neutron diffraction 
and small angle neutron scattering, low temperature specific heat capacity 
measurements, and insitu high pressure spectroscopic studies using 
synchrotron radiation sources. In this talk I will revisit the outstanding 
problems of glass science and present results of our investigations in 
oxide glasses [2-6]. Some of the most notable findings from our laboratory 
are the influence of melt history on the glass forming ability of bismuth 
borate melts, which are found to be metastable liquids. Our studies reveal 
that it is possible to control crystallization in bismuth borate glasses 
by controlling the initial heat treatment given to the melt. These 
findings indicate that the bismuth borate melt is in all probability under 
negative absolute pressure, which causes metastability in the liquid and a 
consequent liquid-liquid phase separation. Lead silicate glasses show an 
interesting effect of melt quenching rate on the devitrification 
properties of glasses. Glasses prepared at higher quenching rate show 
greater tendency towards crystallization on heat treatment. Borate, 
silicate and tellurite glasses containing heavy metal ions like Bi3+, 
Pb2+, Nb5+ and W6+ show an intense optical absorption band just below the 
absorption edge. This band can have useful light emitting properties.
Small angle neutron and X-ray scattering measurements show the existence 
of heterogeneities in lead and bismuth borate glasses in composition 
region where these glasses are believed to be one phase systems. Finally, 
our low temperature specific heat capacity measurements show the existence 
of universal  maxima in Cp/T3 in several borate, tellurite and silicate 
glasses at T~ 10 K. We correlate this maxima with the Boson peak in low 
frequency Raman spectra of glasses.

       [1] P.W. Anderson, Science 267(1995) 1615.
[2] Arshpreet Kaur, Atul Khanna, Carmen Pesquera, Fernando González and 
Vasant Sathe, J. Non Cryst. Solids, 356 (2010)864.
[3] Anu Bajaj, Atul Khanna, Narendra Kulkarni, S. K. Aggarwal, J. Am. 
Ceram. Soc. 92[5] (2009)1036.
[4] Anu Bajaj, Atul Khanna, Banghao Chen, James G. Longstaffe, U-Werner 
Zwanziger, J. W. Zwanziger, Yolanda Gómez and Fernando González, J. Non 
Cryst. Solids 355(2009)45.
[5] Amanpreet Saini ,  Atul Khanna, Vladimir K. Michaelis, Scott Kroeker, 
Fernando González and David Hernández, J. Non Cryst. Solids 355(2009)2323.
[6] Anu Bajaj and Atul Khanna, J. Phys. Condensed Matter 21(2009)035112.