(a) Heated from room temperature to 600 C with a heating rate of 6 C/min
and held on for 60 min.
(b) Heated from 600 C to sintering temperature with a heating rate of 4 C/
min.
(c) Held at sintering temperature for 60 min.
(d) Cooled down from the sintering temperature to 300 C with a cooling rate
of 6 C/min, and furnace-cooled from 300 C to room temperature.
The vacuum was maintained at 1.0 101 Pa during the thermal cycle. After
sintering, the bulk specimens were ground and polished.