Effect of solid particle impact on light transmission of transparent ceramics: Role of the microstructure

• Material transparency correlated to surface degradation.
• Surface degradation correlated to material microstructure.
• Large grain size samples have lower hardness but limit the transparency degradation.

Sand erosion was done on soda lime glass and transparent ceramics such as alumina and magnesium-aluminate spinel with different microstructures. Surface roughness and optical transmission were measured before and after erosion. The increase of surface roughness depends on both the hardness and grain size of the material. Nearly no surface degradation occurs on polycrystalline samples with HV3 > 15 GPa. The decrease of the real in-line transmittance (RIT) after sand blasting is linked to the increase of surface roughness. We have found that this RIT decrease is correlated to three parameters: incident light wavelength, nature of the material (mechanical properties like hardness) and material microstructure. The influence of these will be discussed. Finally, for all polycrystalline ceramics and single crystals, the RIT is only slightly or not altered after sand blasting either at IR or visible wavelengths.