Magnesium oxide powder, production method therefor, thermally-conductive resin composition, thermally-conductive grease, and thermally-conductive coating material

摘要

A magnesium oxide powder has: a median diameter (D₅₀) of 5 to 100 μm; a MgO purity of 98% by mass or more; a Ca compound content of 2% by mass or less in terms of CaO; and when the magnesium oxide powder is immersed in pure water and allowed to stand at 95° C. for 24 hours, a mass ratio of calcium ions to magnesium ions, Ca/Mg, in an aqueous solution of 10 or less.