Silicon nitride-based medium and manufacturing method thereof

Abstract

To provide a silicon nitride-based medium with suppressed variation and improved abrasion resistance and durability and a manufacturing method thereof.SOLUTION: A silicon nitride-based medium satisfies the following requirements (a) to (f), wherein (a) the medium diameter is within the range of 92% or more and 108% or less relative to an average value of the medium diameter; (b) the minimum value among the diameter ratios (minimum diameter / maximum diameter) calculated for each of 100 individual media is 0.8 or more; (c) an internal defect ratio, which is a ratio of a sum total area of defects having a length of 2 μm or more to a medium cross-sectional area, in a medium cross section obtained by polishing 30% to 50% in the medium diameter direction from a medium surface, is 0.5% or less; (d) an apparent density is 3.0 g / cm3 or more; (e) Vickers hardness is 1450HV0.1 or more; and (f) the average crystal grain size is within the range of 0.2 μm or more and 0.7 μm or less.SELECTED DRAWING: Figure 1

Images