Eur. Phys. J. B 51, 507-512 (2006)
https://doi.org/10.1140/epjb/e2006-00253-3

High-temperature behaviour of average structure and vibrational density of states in the ternary superionic compound AgCuSe

¹ Institute for Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany
² Institute for Physics and Power Engineering, Bondarenko Sq.1, 249033 Obninsk, Kaluga reg., Russia
³ CELLS, P.O.B 68, 08193 Barcelona, Spain

Corresponding authors: ^a d_trots@yahoo.com - ^b ans@ippe.ru - ^c mknapp@cells.es - ^d hfuess@tu-darmstadt.de

Received: 11 February 2006
Revised: 27 April 2006
Published online: 22 June 2006

Abstract

Results of simultaneous thermal analysis (STA), synchrotron powder diffraction (in the range 300–973 K) and inelastic neutron scattering (at 285 and 505 K) on non-superionic β- and superionic α-AgCuSe are reported. The sample is stable in argon on heating. The volume change at the superionic phase transition is about 5%. A model for the average structure of α-AgCuSe is proposed. No anomalies in the temperature dependence of the parameters of the average structure were revealed. Ionic conductivity in α-AgCuSe can originate from cation jumps in “skewed” 〈100 〉 directions between nearest-neighbour tetrahedral sites via the peripheries of the octahedral cavities. A correlation between the temperature dependence of the cation redistribution in α-AgCuSe and the temperature dependence of the ionic conductivity is supposed. Various contributions (anharmonic effects, time-average static disorder and phonon-phonon scattering) to the widths of individual phonons upon temperature increase lead to pronounced changes in the neutron-weighted densities of states of β- and α-AgCuSe and accompany the superionic phase transition as well.