Defect strategies for an improved optical quality of transparent ceramics

•Photographic approaches for evidence of defects in transparent ceramics.•Study of color and nature of visible defects.•Low-defect strategies for making polycrystalline transparent sintered ceramics.•Correlation of photographic evidence with transmission spectra and haze data.•Optical quality criteria for major fields of applications.

For the past years most reports on transparent ceramics were focused on improvements of primary parameters like total and in-line transmission, scattering and absorption losses. The present paper directs the attention to previously neglected issues such as the quantified representation of remaining visible defects and the diversity of optical quality criteria for different groups of applications.