The heat capacity and entropy of lithium silicides over the temperature range from (2 to 873) K

This work presents the heat capacities of the four lithium silicide phases Li12Si7, Li7Si3, Li13Si4, and Li22Si5/Li21Si5 as a function of temperature over the range from (2 to 873) K. The measurements were carried out using three different calorimeters. The heat capacities were determined over the range between (2 and 300) K by a relaxation technique using a Physical Properties Measurement System (PPMS) from Quantum Design, within the range between (283 and 353) K by means of a Micro DSC II (Setaram), and data between (303 and 873) K were measured by using a Sensys DSC from Setaram applying the C-p-by-step method. The experimental data are given with an accuracy of (1 to 2)% above T = 20 K and up to 8% below 20 K. The results of the measurements at low temperatures permit the calculation of additional thermodynamic parameters such as the standard entropy as well as the temperature coefficients of electronic and lattice contributions to the heat capacity. The results represent a significant broadening of the data basis for thermodynamic calculations (e.g. CALPHAD) in the Li + Si system. (c) 2013 Elsevier Ltd. All rights reserved.