The equilibrated grain boundary groove shapes for solid succinonitrile (SCN)-liquid SCN Pyrene (PY) were directly observed. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient for solid SCN in equilibrium with the SCN-PY eutectic liquid has been determined to be (5.21 +/- 0.26) x 10(-8) K m with numerical method. The solid-liquid interface energy for the solid SCN in equilibrium with the SCN-PY eutectic liquid has been obtained to be (9.58 +/- 0.96) x 10(-3) J m(-2) from the Gibbs-Thomson equation. The grain boundary energy of SCN rich phase of the SCN-PY system has been determined to be (18.30 +/- 2.38) x 10(-3) J m(-2) from the observed grain boundary groove shapes. The thermal conductivity ratio of the liquid phase to the solid phase-for SCN-3 mol% PY alloy has also been measured. (C) 2005 Elsevier B.V. All rights reserved.