A machined ceramic article having an initial surface defect density and an initial surface roughness is provided. The machined ceramic article is heated to a temperature range between about 1000° C. and about 1800° C. at a ramping rate of about 0.1° C. per minute to about 20° C. per minute. The machined ceramic article is heat-treated in air atmosphere. The machined ceramic article is heat treated at one or more temperatures within the temperature range for a duration of up to about 24 hours. The machined ceramic article is then cooled at the ramping rate, wherein after the heat treatment the machined ceramic article has a reduced surface defect density and a reduced surface roughness.