Annealing studies of chromium implanted silicon nitride ceramics

The effect of chromium implantation and subsequent annealing
on the hardness and wear behaviour of a silicon nitride-based ceramic is
investigated. Implantation energies were 200, 400, 1000 and 2000 keV, the
fluence was 1017 Cr+ ions cm-2 in all cases. The annealing temperatures
were 800 C, 1000 C and 1200 C. The phase composition was determined with
X-ray diffraction. Annealing at 800 C does not affect the crystal structure.
At 1000 C the -Si3N4-phase is formed for 1 and 2 MeV implantation energy.
At 1200 C, Cristobalite and Keiviite are formed at the lower implantation
energies; at higher energies -Si3N4 is formed. We discuss the phase formation
for the different implantation energies and annealing temperatures and
the relationship with the observed hardness and wear.