Shift of Glass Transition Temperature under High Pressure for Ge₂₀Te₈₀ Glass

Abstract:

Amorphous solids prepared from their melt state exhibit glass transition phenomena upon heating. Derivatives of volume like viscosity, specific heat and thermal expansion coefficient show rapid changes at the glass transition temperature (T_g). In general, application f high pressure increases the T_g (a positive dT_g/dP). This positive dTg/dP has been well understood with the Free Volume and Entropy models. However, there are few exceptions where a negative dT_g/dP has been observed. It has been proposed that the glasses which undergo negative thermal expansion can exhibit a negative dT_g/dP. In this study, electrical resistivity of semiconducting Ge₂₀Te₈₀ glass at high pressures as a function of temperature has been measured in a Bridgman anvil apparatus. Electrical resistivity showed a pronounced change at T_g. The pressure dependence of T_g (dT_g/dP) shows a decreasing trend (-dT_g/dP). Chalcogenide glasses like Se, As₂Se₃ and As₃₀Se₃₀Te₄₀ show a positive dT_g/dP in contradiction to the present observation of negative dT_g/dP. A model proposed by deNeufville and Rockstad finds a linear relationship between T_g and the optical band gap (E_g) when they are grouped according to their connectivity (Z_av).Application of high pressure decreases the interatomic distance which in turn decreases the separation between the valence and conduction bands (optical band gap). This reduction in optical band gap shifts the glass transition to lower values. It is also suggested that the sign of the pressure derivative of T_g can be negative (-dT_g/dP) if the thermal expansion coefficient is negative. Inelastic neutron diffraction studies show a negative thermal expansion coefficient for most of the Te based chalcogenide glasses. Hence, Ge₂₀Te₈₀ glass is uniquethat its pressure dependence of T_gobeys both thermodynamic and the T_g-E_g-Z_av models.

• Periodical: Key Engineering Materials (Volume 702)
• Pages: 43-47
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.702.43
• Online since: July 2016
• Authors: K. Ramesh*, N. Naresh, Pumlianmunga Pumlianmunga, E.S.R. Gopal
• Keywords: Chalcogenide Glasses, Electrical Resistivity, Glass Transition, High Pressure

References

[1] A.R. Cooper, The ubiquitous glass transition, J. Non-Cryst. Solids, 95 & 96 (1989) 1- 14.

[2] D. Turnbull, M.H. Cohen, On the Free Volume model of the liquid glass transition, J. Chem. Phys. 52 (1970)3038 - 3041.

[3] G. Adam, J.H. Gibbs, On the temperature dependence of cooperative relaxation properties in glass forming liquids, J. Chem. Phys. 43 (1965) 139 - 146.

DOI: 10.1063/1.1696442

[4] Frank H. Stillinger, P. Debenedetti, Glass transition thermodynamics and kinetics, Annu. Rev. Condens. Matter Phys. 4 (2013) 263 - 85.

DOI: 10.1146/annurev-conmatphys-030212-184329

[5] J. Jackle, Models of the glass transition, Rep. Prog. Phys. 49 (1986) 171-231.

DOI: 10.1088/0034-4885/49/2/002

[6] K.J. Rao, The phenomenon of glass transition, Bull. Mater. Sci. 1 (1979) 191 - 193.

[7] N.S. Bagdassarov, J. Maumus, B. Poe, A.B. Slutsky, V.K. Bulatov, Pressure dependence of Tg in silicate glasses from electrical impedance measurements, Phys. Chem. Glasses, 45 (2004) 197. - 214.

[8] B.A. Joiner, J.C. Thompsun, Glass transition temperature shift under pressure for some semiconducting glasses, J. Non-Cryst. Solids, 21(1976) 215 - 224.

DOI: 10.1016/0022-3093(76)90042-9

[9] K. Ramesh, Pressure dependence of glass transition in As2Te3 glass, Phys. Chem. B 118 (2014) 8848–8853.

[10] E. Williams, C.A. Angell, Pressure dependence of the glass transition temperature in ionic liquids and solutions. Evidence against free volume theories, J. Phys. Chem. 81(1977) 232 - 237.

DOI: 10.1021/j100518a010

[11] J.M. O'Reilly, The effect of pressure on glass temperature and dielectric relaxation time of polyvinyl acetate, J. Polym. Sci. 57(1962) 429 - 444.

DOI: 10.1002/pol.1962.1205716534

[12] C.A. Angell, E. Williams, K.J. Rao, J.C. Tucker, Heat capacity and glass transition thermodynamics for zinc chloride. A failure of the first Davies-Jones relation for dTg/dP, J. Phys. Chem. 81(1977) 238 – 243.

DOI: 10.1021/j100518a011

[13] Z.U. Borisova, Glassy Semiconductors; Plenum Press: New York, (1981).

[14] J.P. deNeufville, H.K. Rockstad, Proc. 5th Int. Conf. on Amorphous and Liquid Semiconductors; eds., J. Stuke, J.; Brenig, W. 1974, p.419.

[15] T.K. Mondal, S. Murugavel, S. Asokan, An automated, externally heated opposedanvil high pressure–high temperaturesystem for electrical resistivity studies. Rev. Sci. Instrum. 70 (1999) 165 - 170.

DOI: 10.1063/1.1149559

[16] S.R. Ovshinsky, H. Fritzsche, Reversible structural phase transformations in amorphous semiconductors for memory and logic, Met. Trans. 2(1971) 641 - 645.

DOI: 10.1007/bf02662715

[17] M. Goldstein, Some thermodynamic aspects of the glass transition: Free Volume, Entropy and Enthalpy Theories, J. Chem. Phys. 39 (1963) 3369 - 3374.

DOI: 10.1063/1.1734202

[18] P.K. Gupta, Negative pressure dependence of viscosity, J. Am. Ceram. Soc. 70(1976)4136 – 4140.

[19] H.A. Schneider, B. Rudolf, K. Karlou, H.J. Cantow, Pressure influence on the glass Transition of polymers and polymer blends, Polym. Bull. 32(1994) 645-652.

DOI: 10.1007/bf00973914

[20] G. Parthasarathy, E.S.R. Gopal, Effect of high pressure on chalcogenide glasses, Bull. Mater. Sci. 7(1985) 271 – 302.

DOI: 10.1007/bf02747579