Study On The Low Temperature Processing On Synthesis Of Near Ultraviolet Excited Borate Phosphor By Solid State Method

The currently commercial white light emitting diodes(W-LEDs)are obtained mainly by combining a blue-emitting GaN chip with a yellow-emitting yttrium aluminum garnet(YAG)doped Ce3+ phosphor.This approach often lead to non-uniform white light,high correlated color temperature,low color-rendering index and especially too much blue light is not good for human health,which is unsuitable for the indoor lighting application.In order to overcome these disadvantages,developing an efficient near-ultraviolet(near-UV)exciting tricolor phosphors(blue,green and red)for indoor lighting has become a hot topic in recent years.Rare earth doped borate a great potential luminescent material due to its diversification of synthetic methods,low synthesis temperature,stable performance and low cost.Conventional high-temperature solid state reaction has the advantages of simple fabrication and short cycle,as well as the obtained phosphorus is high luminous intensity and pure color,thus,it is the best choice to achieve the mass production.However,high preparation temperature,high energy consumption and high cost seriously restrict to the development of its mass production and commercialization.Therefore,it is of great significance to study the synthesis of Near-UV exciting Borate Phosphors by low temperature solid-phase method.In this thesis,low temperature synthesis of near ultraviolet excited borate phosphor by solid state method has been studied,as well as the corresponding optical performance has been investigated.The main results are as follows:1.A series of Sr2MgB2O6:Tb3+,Li+ phosphors were synthesized at 960℃ by conventional solid-state reaction method.The Tb3+ ion is often known as activator of the green-emitting phosphor,The Li+ ion was served as charge compensator.The concentration quenching occur at Tb3+ concentration in excess of x=0.09,Sr2MgB2O6:Tb3+,Li+ is stable performance.The optimal excitation wavelength is 368 nm(7F6-5G5)and the maximum emission wavelength is 545 nm(5D4-7F5),the chromaticity coordinates is(0.262,0.583).2.A series of Li2AlBO4:Eu3+phosphors were synthesized at 820℃ by conventional solid-state reaction method.The Eu3+ ion is often known as activator of the red-emitting phosphor.The concentration quenching occur at Eu3+ concentration in excess of x=0.11,the optimal excitation wavelength is 394 nm(7F0-5L6)and the maximum emission wavelength is 593 nm(5D1-7F3),the chromaticity coordinates is(0.508,0.38).3.A series of SrBi2B2O7:Eu3+ phosphors were synthesized at 730 ℃ by conventional solid-state reaction method.The Eu3+ ion is often known as activator of the red-emitting phosphor.The concentration quenching occur at Eu3+concentration in excess of x=0.29,the optimal excitation wavelength is 394 nm(7F0-5L6)and the maximum emission wavelength is 614 nm(5D0-7F2),the chromaticity coordinates is(0.527,0.343).4.A series of Li3AIB2O6:Eu3+ phosphors were synthesized at 730℃ by conventional solid-state reaction method.The Eu3+ ion is often known as activator of the red-emitting phosphor.The concentration quenching occur at Eu3+concentration in excess of x=0.09,the optimal excitation wavelength is 393 nm(7F0-5L6)and the maximum emission wavelength is 614 nm(5D0-7F2),the chromaticity coordinates is(0.536,0.373).5.A series of Li3AlB2O6:Tb3+ phosphors were synthesized at 730℃ by conventional solid-state reaction method.The Tb3+ ion is often known as activator of the green-emitting phosphor.The concentration quenching occur at Eu3+concentration in excess of x=0.11,the optimal excitation wavelength is 377 nm(7F6-5G6)and the Aaximum emission wavelength is 543 nm(5D4-7F5),the chromaticity coordinates is(0.263,0.609).6.A series of Li3AlB2O6:Tb3+,Eu3+ phosphors were synthesized at 730℃ by conventional solid-state reaction method.The Tb3+ and Eu3+ ions are used as activators of the fluorescent powder.Under the near UV irradiation,the energy absorbed by Tb3+ normally emits light at 488 nm(transition by 5D4-7F6)and 543 nm(5D4-7F5),but here due to the energy band overlap between Tb3+ and Eu3+ in Li3AlB2O6 crystal,the inherent radiative transition of Tb3+ didn’t occur,but the energy was transferred directly to Eu3+,resulting in a red light emission at 594nm and 614nm,and moreover the luminous intensity was greatly increased..Therefore,co-doped Li3AlB2O6:Tb3+,Eu3+ is a kind of red phosphor with excellent performance.