Research On The Luminescence Properties Of Single-phased Ca₁₀Na?PO₄?₇ And Sr₆Ca₄?PO₄?₆F₂ Phosphor For Nuv-pumped White LEDs

White light emitting diodes?WLED?are widely used in the fields of street lighting,traffic lights,display screens,small size LCD backlight,medical light source and so on.It is known as a new generation of solid-state sources,since the merits of environmentally friendly,anti-seismic,long lifetime,energy conservation,short response time.It is used as the main lighting pattern in 21st century.The most common way to realize WLED device is the method of phosphor-converted WLED,which is the combination of phosphor and diode chip.Therefore,the property of phosphor has a decisive influence on WLED device.Currently,the simplest and the most mature way to realize WLED is fabricated with blue LED chip and yellow-emitting phosphor.Due to the lack of red light component,the device has a high correlated color temperature,a low color rendering index;the conversion efficiency of phosphor for blue light is relatively low.Therefore,the efficiency of WLED was influenced by blue LED chip and phosphor.The near ultraviolet LED chip and the red,green,blue three-colored phosphors which can be excited by ultraviolet light are fabricated into white LED.Due to the re-absorption of blue light by green light and red light emitting phosphors and the problem of the ratio of three color phosphors,the luminous efficiency of WLED is low.Therefore,in order to improve the above problems,the main content of this paper is to prepare single-phase white light-emitting phosphors which can be stimulated by ultraviolet or near ultraviolet light.The high-temperature solid-state method is a common way to synthesize commercial phosphors,due to the merits of convenient operation,low cost,high yield and good filling;phosphate material has the advantages of low calcination temperature,excellent thermal stability and stable chemical properties,so it is used as matrix material for phosphor.In this paper,Ca₁₀Na?PO₄?₇,Sr₆Ca₄?PO₄?₆F₂ were used as matrix,and a series of phosphors were synthesized by high-temperature solid-state method.The samples were characterized by XRD,DRS,SEM and PL,and ET and thermal stability were also studied.The specific contents include the following parts:?1?Under the CO atmosphere,a series of Ca₁₀Na?PO₄?₇:xCe³⁺phosphors were synthesized by high temperature solid state method.With the increase of Ce³⁺doping concentration,the luminescence intensity of phosphor increases gradually.When the concentration of Ce³⁺x=15mol%,the PL intensity of phosphor reaches the maximum value,and then increases Ce³⁺doping concentration,and the PL intensity was decreased.In accordance of Dexter's theory,the concentration quenching mechanism of Ce³⁺is the electric dipole-dipole interaction.?2?A series of Ca₁₀Na?PO₄?₇:0.15Ce³⁺,y Tb³⁺,zMn²⁺was synthesized by high temperature solid state method.By adjusting the ratio of doping concentration of Tb³⁺,Mn²⁺,we have synthesized white light-emitting phosphor with the color coordinates?0.333,0.313?,and the correlated color temperature 5460K.The internal and external quantum efficiency are 76.79%and 54.11%,respectively.At 150^oC,the luminescence intensity of Ca₁₀Na?PO₄?₇:Ce³⁺,Tb³⁺,Mn²⁺is51.78%compared to that at room temperature.?3?Under the CO atmosphere,a series of Sr₆Ca₄?PO₄?₆F₂:Eu²⁺,Mn²⁺has synthesized by high temperature solid state method.The Eu²⁺optimal doping concentration is 3mol%.With the increase of Mn²⁺concentration,the emission color of Sr₆Ca₄?PO₄?₆F₂:Eu²⁺,Mn²⁺changes from blue to warm white.We have synthesized white light light-emitting phosphor with the color coordinates?0.326,0.318?,and the color temperature 5823K,respectively.