Synthesis And Luminescent Mechanisms Of M₃Al₂O₆:Ce³⁺,Mn²⁺（M=Ca,Sr） Phosphors

Thanks to the numerous virtues of aluminate phosphors,they are one important class of novel and effficient luminescence materials.Due to their high quantum efficiency in the visible region,excellent color stability and low manufacturing costs,they have attracted enormous interest in recent years.In this paper,we use Ca₃Al₂O₆ as a host to synthesize a series of Ce³⁺and Mn²⁺doped alkaline earth aluminate phosphors by conventional solid state reaction.And researches on the phosphors’crystal structure and luminscence properties have been carried out.The detailed contents and results are as follows:1.A series of Ca_2.76-xSr_xAl₂O₆:0.12Ce³⁺,0.12 Li⁺（0≤x≤2.76）solid solution phosphors are synthesized by conventional solid state reaction.Here we report the structural phase transformation from Ca₃Al₂O₆ phase to Sr₃Al₂O₆ phase with Sr²⁺substitution for Ca²⁺in the phosphors.Ce³⁺will redistribute among different Ca²⁺sites over the composition range0≤x≤2.76,which can tune the emission band.The emission peaks of Ce³⁺excited at 365 nm shift from 420 nm to 470 nm as the Sr²⁺contents change,while that of the PL spectra excited at 305 nm stays unchanged at470 nm.The energy transfer from blue-emitting Ce³⁺to a cyan one was verified in terms of the PLE spectra and decay curves of the phosphors.2.A series of color-tunable Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Li⁺phosphors were synthesized by a high-temperature solid-state reaction.The phase formation and morphology characterization were identified by XRD patterns and SEM images.To further investigate the crystal structure of the host,Rietveld structural refinement of Ca_2.5Sr_0.5Al₂O₆ has been performed using the general structure analysis（GSAS）program.Under the excitation wavelength at 365 nm,a dramatic blue shift from 470 nm to 420 nm of the emission peak was observed on an increase of Ce³⁺content,but it showed little change at the excitation of 305 nm.Furthermore,a new PL spectrum peaked at 500 nm was found under the excitation at 400 nm.The relationship between the luminscence properties and crystal structure has been investigated in detail.3.A series of single-phase phosphor,Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Li⁺,Mn²⁺was prepared by solid-state reaction,which can provide white-light emission.The phase formation,photoluminscence properties as well as the energy transfer from Ce³⁺to Mn²⁺ions have been studied in detail.The different decreasing trends of blue and cyan emissin components were observed in Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Li⁺,Mn²⁺phosphors with the increase of Mn²⁺content,suggesting different energy transfer efficiencies from blue-and cyan-emitting Ce³⁺to Mn²⁺.Finally,phosphors with high color-rendering index（CRI）values are realized by adjusting the doping contents of both Ce³⁺and Mn²⁺.