Silicon nitride (Si₃N₄) is a covalent compound with high hardness, wear resistance, thermal stability, and chemical stability. It can withstand high temperatures, with a decomposition temperature of about 1900°C and a practical usage temperature up to 1400°C. It has excellent mechanical strength, with a bending strength exceeding 980 MPa, and can endure high-temperature thermal shock without cracking. Silicon nitride is highly resistant to most inorganic acids, many organic substances, and molten non-ferrous metals, and also exhibits excellent electrical insulation and optical transparency.