https://doi.org/10.1051/epjap:1998239
Electrical and optical investigations of Rb2ZnCl4 crystals in the vicinity of the incommensurate phase
Physics Department, Faculty of Science, Assiut University, Assiut, Egypt
Corresponding author: assiut@frcu.eun.eg
Received:
27
February
1998
Revised:
28
May
1998
Accepted:
28
May
1998
Published online: 15 October 1998
Temperature dependence of the dielectric constant ϵ and the
electrical resistivity ρ of Rb2ZnCl4 (RZC) along the three
crystallographic axes were measured between 260 and 360 K. The electrical measurements
clearly reveal the paraelectric incommensurate phase around 303 K. Peaks in the
dielectric constants ϵa and ϵb were observed at this transition
temperature. The results of the electrical resistivity were analyzed and the activation
energies of conduction at different temperature regions were evaluated. The dependence
of the absorption coefficient α on the photon energy and on temperature near the
fundamental absorption edge was measured. Exponential dependence of that coefficient
according to the Urbach's rule was observed and the Urbach parameters were determined
and their temperature dependence was investigated. The temperature gradient of the band
gap reveals an anomaly at the incommensurate paraelectric
phase. The indirect band gap was shifted towards the longer wavelength (red shift)
with increasing temperature. This behaviour could be interpreted in terms of electron
lattice interaction and crystal field splitting.
PACS: 64.70.Rh – Commensurate incommensurate transitions / 78.20.-e – Optical properties of bulk materials and thin films
© EDP Sciences, 1998