Tailoring optical properties of (Ce,Pr)O2-δ·(La,Sm,Y)2O3 high entropy oxides by substituting Pr with Gd or Dy for multi-wavelength emission applications

High-entropy oxides (HEOs) has generated considerable research interest because of their novel inherent properties and tuneable functionality. In this study, reactive sintering method was used to synthesize HEOs with three different compositions (Ce,RE)O 2-δ · (La,Sm,Y) 2 O 3 [RE=Pr], and CeO 2-δ · (RE,La,Sm,Y) 2 O 3 [RE=Gd,Dy]. Replacement of Pr cation with Gd or Dy in the synthesized compositions significantly increased the band gap value from 1.8 eV to 3.13 eV and 3.18 eV respectively. The broader band gap improved luminescent properties of bulk ceramic samples. Strong emissions originating from Ce 3+ , Dy 3+ and Sm 3+ in Dy-containing HEO and from Ce 3+ , Gd 3+ and Sm 3+ in Gd- containing HEO were observed at multiple wavelengths through entire visible region. Under multi-wavelength excitation, effective regulation of the emission colour was achieved, resulting in enhanced photoluminescence performance. The prepared HEOs, CeO 2-δ · (RE,La,Sm,Y) 2 O 3 [RE=Gd,Dy] can be considered as a novel materials for white light application (WLED) with excitation at multiple wavelengths and tuneable emission.