Crystal structure analysis and evidence of mixed anion coordination at the Ce3+ site in Y3Al2(Al,Si)3(O,N)12 oxynitride garnet phosphor

Abstract

The structural and luminescence properties of Ce³⁺-doped Y₃Al_4.75Si_0.25O_11.75N_0.25 oxynitride garnet (YASiONG:Ce) phosphor are investigated by neutron powder diffraction (NPD) and spectroscopic measurements, respectively. The obtained NPD patterns confirmed the presence of N atoms in YASiONG:Ce by Rietveld structural refinement for the first time. In addition, we studied the structure and bond lengths of YASiONG and compared the parameters with those of Y₃Al₅O₁₂ (YAG) using two different models and experimental NPD data. In the photoluminescence (PL) and PL excitation spectra of the YASiONG:Ce phosphor measured at 50 K, additional excitation and emission bands of Ce³⁺: 4f → 5d₁ appeared at longer wavelengths compared with the YAG:Ce phosphor. The additional bands can be attributed to the 4f → 5d₁ transition of Ce³⁺ at the dodecahedral site with one N³⁻ and seven O²⁻ coordination.