Creep deformation behavior during densification of ZrB 2 -SiBCN ceramics with ZrO 2 additive

ZrB 2 -SiBCN ceramics with ZrO 2 additive are hot-pressed under a constant applied pressure. The densification behavior of the composites is studied in a view of creep deformation by means of the Bernard-Granger and Guizard model. With determination of the stress exponent ( n ) and the apparent activation energy ( Q d ), the specific deformation mechanisms controlling densification are supposed. Within lower temperature ranges of 1300–1400 °C, the operative mechanism is considered to be grain boundary sliding accommodated by atom diffusion of the polymer-derived SiBCN ( n = 1, Q d = 123±5 kJ/mol) and by viscous flow of the amorphous SiBCN ( n = 2, Q d = 249±5 kJ/mol). At higher temperatures, the controlling mechanism transforms to lattice or intra-granular diffusion creep ( n = 3–5) due to gradual consumption of the amorphous phase. It is suggested that diffusion of oxygen ions inside ZrO 2 into the amorphous SiBCN decreases the viscosity, modifies the fluidity, and contributes to the grain boundary mobility.