In this paper, we investigated the temperature dependence and optical contrast variations of a nonlinear optical material. The experiments were performed using the close and open aperture z-scan technique using a CW laser beam at 632.8 nm. The nonlinear optical behavior is attributed to thermo-optical effect. The absorption variation as function of temperature is studied. The linear absorption variation induces changes in nonlinear refraction. The nonlinear optical properties of the samples reduce when the temperature increases. (C) 2011 Elsevier B.V. All rights reserved.