The temperature dependence of the Gruneisen parameters of MgSiN2, AlN and β-Si3N4

The temperature dependence of the Gruneisen parameter of MgSiN2 (80-1600 K), AlN (90-1600 K), and beta -Si3N4 (300-1300 K) was evaluated from thermal expansion, elastic constants and heat capacity data of these materials. For all compounds the Gruneisen parameter increases as a function of the reduced temperature approaching a constant value at high temperatures (T/theta greater than or equal to 0.8). The high temperature limit of the Gruneisen parameter of the wurtzite type materials MgSiN2 and AlN is about the same (0.98 and 0.95, respectively) whereas these are much higher than that of the phenacite beta -Si3N4 (0.63). This behaviour can be understood quantitatively from the relation between the Gruneisen parameter and the bond parameter W as established by Slack. (C) 2001 Elsevier Science Ltd. All rights reserved.