Fused silica (amorphous SiO₂) and quartz ceramics offer the lowest thermal expansion of any solid material (≈0.55×10^−6/K for synthetic fused silica) combined with high optical transparency from UV through IR.
That near-zero expansion makes it the reference material for precision metrology stages, photolithography reticles, telescope mirrors and any application where dimensional stability across temperature swings is critical. Fused silica is also essentially free of thermal stress during rapid heating or cooling, giving it unlimited thermal-shock resistance in practice.