Synthesis Of Double Perovskite Red Phosphors For White LEDs And Their Properties

White Light Emitting Diodes(WLED),which are consider as the fourth generation of lighting,is leading a new era of green lighting due to the advantages of small size,energy saving,environmental friendly,high luminous efficiency,etc.However,there are still challenges for phosphor-convert LEDs in colour hue and stability because the red phosphors with high emission intensity and high stability are sparse for LED chips.Therefore,the research on red phosphors is urgent so that WLED can achieve excellent luminescent.A double perovskite red phosphor Ba2CaMoO6:Eu3+was synthesized by high temperature solid state method.The reaction of the matrix Ba2CaMoO6 was studied in the preparation process According the thermal analysis and theoretical calculation,it was found that the actual weight loss of the 20.58%was close to the theoretical weight loss 20.74%.The appropriate pre-heat temperature was found,the matrix first calcined at 700? for 1 h,then heated to 1050? for 2 h,finally to 1300? for 4 h.The red phosphor crystal structure belongs to the cubic crystal with the space group Fm-3m.The effects of different charge compensators(M+=Li+,Na+,K+)on the luminescent properties of the samples were investigated.According to the results,the luminescent properties of all the samples with charge compensators were improved.As is well known,with the increase of the atomic number,the ionic radii increase in the order of Li+<Na+<K+.The samples doped with Li+,increased by 1.75 times,doped with Na+,increased by 2.05 times,and doped with K+,increased by 1.63 times.Although K+ Ionic Radius(1.64A)is close to Ba2+ Ionic Radius(1.61A),Na+ Ionic Radius(1.53A)and is slight small than Ba2+ Ionic Radius(1.61A)which could more easily embedded into lattice.Hence,monovalent ion Na+ as charge compensator could obtain the great enhancement of the orange red emission,which is well consistent with the experimental results.The effects of W and Mo on the structure and luminescence properties were investigated to improve luminescent properties further.According to XRD analysis,Ba1.75Eu0.1Na0.15CaWyMO1-yO6 series of red phosphor belongs to the cubic crystal with space group Fm-3m,several extra peaks were found corresponding to scheelite BaMoO4.It was found that the series phosphor exhibits the best luminescence properties when y is 0.9.Ba2-2zEuzNazCaW0.9Mo0.1O6 series phosphor was prepared by high temperature solid-state reaction.At low concentration,the phase structure was pure and belonged to the cubic crystal system with space group was Fm-3m.At high concentration,there were weak phase Scheelite BaWO4 and CaMoO4.According to the structural analysis,Eu3+ does not enter the A-position,but enters the B-site,it is illustrated that the crystal symmetry decreases.The intensity of the luminescence increases with the increase of Eu3+,but there is no obvious concentration of quenching phenomenon.The peak of the fission line coincides with the emission spectrum.A total of 8 peaks are fitted,which means that the phosphor of the system is not strictly symmetrical,and the color purity is gradually increased with the increase of Eu3+ concentration.