Near-Infrared Luminescence from Porcelain Glazes Originates from Neodymium Ion

Porcelains are inorganic, nonmetallic solids prepared by firing and subsequent cooling. They are usually covered by a thin layer of glaze, which often exhibits a strong luminescence near 880 nm with near-infrared 785 nm excitation. In a previous study, we showed that the band shape of the luminescence depends on the processing temperature, indicating that the luminescence band shape has potential as a nondestructive probe for analyzing a glaze. However, the origin of the luminescence was previously unclear. In this study, we found that the luminescence is ascribed to feldspar, which is a major raw material in glazes. Furthermore, an elemental analysis using inductively coupled plasma optical emission spectroscopy detected neodymium (Nd) and praseodymium (Pr) in the feldspar samples. Luminescence measurements of glaze samples containing additional Nd3+ and/or Pr3+ demonstrated that the luminescence is due to Nd3+. We also compared the luminescence spectra of ancient shards found in the Arita and Seto areas of Japan. The band positions differed between the two different ceramic production areas, suggesting that the luminescence from Nd3+ can be useful for identifying the origin of ancient ceramics.