Hexagonal boron nitride (h-BN)

In addition, h-BN has a high thermal stability, which means it can withstand high temperatures without breaking down. This makes it an ideal material for use in high-temperature environments.

Furthermore, h-BN has a low coefficient of thermal expansion, which means it doesn't expand and contract greatly with temperature changes. This property helps to prevent thermal stresses and maintain dimensional stability.

Overall, the combination of high thermal conductivity, thermal stability, and low thermal expansion make h-BN an excellent choice for use as an insulating material in applications that require efficient heat transfer and high-temperature stability.