Materials Science Forum, Vol.299, 35-43, 1999
Translucent polycrystalline alumina: Influence of roughness and thickness on in-line transmittance
Translucent polycrystalline alumina ceramic has its main application as discharge are tube in high pressure sodium lamp, Translucent polycrystalline alumina bodies with two different additive compositions were produced by a conventional pressureless sintering route (1850 degrees C for 3h under vacuum). Different surface conditions (roughness) and thickness were produced by grinding and polishing the samples. Roughness (Ra and Ry) and in-line transmittance of the samples were measured. A great influence of surface condition on the transmittance was observed. The influence of thickness (0.4 similar to 1.6mm) of polished samples on in-line transmittance was evaluated, An exponential correlation between transmittance and sample thickness was observed. For comparison, the same analysis was made on single crystal alumina (sapphire) discs.