Luminescence properties of silicate apatite phosphors M2La8Si6O26:Eu (M = Mg, Ca, Sr)

Abstract Europium ions doped M 2 La 8 Si 6 O 26 (M = Mg, Ca, Sr) silicate apatite phosphors have been synthesized by using solid-state reaction method, post-treated in a reducing atmosphere and studied by optical spectroscopy techniques. It has been revealed that the emission spectra from all the synthesized samples contain a set of spectral lines due to the 4f – 4f transitions of Eu 3+ ions, which predominantly occupy the A2 sites of C s symmetry in the apatite structure. Efficient conversion of Eu 3+ to Eu 2+ has been achieved in a reducing H 2 /Ar atmosphere for the Mg 2 La 8 (SiO 4 ) 6 O 2 apatite due to the charge compensation mechanism by oxygen vacancies. This apatite possesses broadband yellow emission with the band maximum at 560 nm and the luminescence decay time τ 2+ transitions and this yellow luminescence band can be efficiently excited by near-UV to blue light (300–450 nm). It is assumed that by optimization of the europium concentration and Eu 3+ /Eu 2+ ratio promising single-phase phosphors can be obtained for warm white LEDs having high color rendering indexes.