LaSr2AlO5, a Versatile Host Compound for Ce3+-Based Yellow Phosphors: Structural Tuning of Optical Properties and Use in Solid-State White Lighting

Cerium-doped lanthanum strontium aluminum oxide LaSr2AlO5:Ce3+ has recently been identified by us as a viable yellow phosphor that in conjunction with a blue-emitting diode can be used in solid-state white lighting sources. In this study, we present the energy level structure relevant to the luminescence process within LaSr2AlO5:Ce3+, based on crystal structure determination by powder X-ray diffraction and the peak deconvolution of excitation and emission spectra. We also establish the versatility of the phosphor host LaSr2AlO5 by examining isovalent substitutions of all three cation types in the structured Gd or Tb for La, Ca or Ba for Sr, and B or Ga for Al. All the above cation substitutions/solid solution are achieved to the full extent except when Ca (for Sr) or B (for Al) are chosen as substituent. Optical properties of the prepared Ce3+ phosphors are found to depend on the rare-earth metal-oxygen distances and the lattice ionicity. Among die compounds studied here, excitation maxima range between 435 and 453 nm and emission maxima between 552 and 577 mm, which are promising for delicate color control in InGaN-based blue-pumped, yellow-emitting phosphors for solid-state white fighting. Prototype light-emitting diodes have been fabricated by formulating various phosphor compositions obtained in this study, and their electroluminescence properties are presented.