The temperature dependence of the Gruneisen parameters of MgSiN2, AlN and beta-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 reduc ed temperature approaching a constant value at high temperatures (T/theta g reater than or equal to 0.8). The high temperature limit of the Gruneisen p arameter 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 quantitative ly from the relation between the Gruneisen parameter and the bond parameter W as established by Slack. (C) 2001 Elsevier Science Ltd. All rights reser ved.