what type of bonding gives ceramics their strength?
It depends on the ceramic. Usually some combination of ionic bonding involving small, multiply charged, ions such as Mg2+ and/orAl3+, and a network of polar covalent bonding, often involving silicon and oxygen. All ceramics derived from clay are of this type. But some ceramics, such as silicon nitride, just work by a network of very strong, partly polar,covalent bonds.
Ionic bonding, in engineering production process we are add a catalyst to lower the bond to covalence bond so it could easily be melt.
