Crystal Structure and Photoluminescence Properties of Red‐Emitting Ca ₉ La 1−x (VO ₄ ) ₇ :xEu ³⁺ Phosphors for White Light‐Emitting Diodes

This paper reports the crystal structure and photoluminescence properties of Ca 9 La 1− x (VO 4 ) 7 : x Eu 3+ ( x =0–1) phosphors synthesized at various temperatures (850°–1350°C) in air for 12 h using traditional solid‐state reaction method. Rietveld refinement of powder X‐ray diffraction pattern of Ca 9 Eu(VO 4 ) 7 indicated that the structure of Ca 9 Eu(VO 4 ) 7 consisted of [VO 4 ] tetrahedra and Ca/Eu atoms were filled in the space between the tetrahedral groups, with a random distribution for Eu 3+ ions on four individual Ca crystallographic sites. A major intense sharp emission line, locating at 613 nm under 465 nm excitation, was observed due to the 5 D 0 − 7 F 2 transition of Eu 3+ within 4 f configurations, which originates from the lower site symmetry in Ca 9 La 1− x (VO 4 ) 7 : x Eu 3+ . Interestingly, no concentration quenching was found in this phosphor, and thermal quenching was nearly not affected by Eu 3+ concentration. The experimental results suggested that this novel red‐emitting phosphor could be applied in white light‐emitting diodes.