Photoluminescence of Cerium‐Doped α‐SiAlON Materials

Cerium‐doped α‐SiAlON (M _x Si _{12−( m + n )} Al _{m + n} O _n N _{16– n} ) materials have been prepared by gas‐pressure sintering and post‐hot‐isostatic‐press (HIP) annealing, using four powder mixtures of α‐Si ₃ N ₄ , AlN, and either (i) CeO ₂ , (ii) CeO ₂ + Y‐α‐SiAlON seed, (iii) CeO ₂ + Y ₂ O ₃ , or (iv) CeO ₂ + CaO. Cerium‐containing CeAl(Si _{6– z} Al _z )(N _{10– z} O _z ) (JEM) phase, rather than Ce‐α‐SiAlON phase, forms in the sample with only CeO ₂ , whereas a single‐phase α‐SiAlON generates in samples with dual doping (CeO ₂ + Y ₂ O ₃ and CeO ₂ + CaO). On ultraviolet‐light excitation, JEM gives one broad emission band with maximum at 465 nm and a shoulder at 498 nm; α‐SiAlON shows an intense and broad emission band that peaks at 500 nm. The unusual long‐wavelength emissions in JEM and α‐SiAlON are due to increases in the nephelauxetic effect and the ligand‐field splitting of the 5 d band, because the coordination of Ce ³⁺ in JEM and α‐SiAlON is nitrogen enriched.