Synthesis And Spectrum Property Of Rare Earth Doped Novel Phosphors

The white light emitting diodes?LEDs?,which presents excellent properties such as energy conservation,environmental protection and high efficiency,have been considered to be the fourth generation light source.The commercial white LEDs are made by the combination of blue LED chip and yellow phosphor.However,the color rendering index?CRI?of this LED is low,owing to the absence of red light component which is one of the three primary colours in producing white light.For solving the problems mentioned above,the subject is focused on the two following sections:?1?investigating superior red phosphors to combine with the blue or n-UV LED chips;?2?developing the single-phase white phosphors which can be efficiently excited by n-UV light.A series of red phosphors Ba₃Gd?PO₄?₃:Eu³⁺?GdNbO₄:Sm³⁺ and white phosphor GdNbO₄:Dy³⁺ with different concentrations were synthesized by high-temperature solid-state method,and the properties of luminescence and color rendering index are analyzed in detail,the main content and results include:?1?The crystal structure of the Ba₃Gd?PO₄?₃:Eu³⁺ products was analyzed by X-ray diffraction.It was confirmed that all samples exhibited pure phase as Ba₃Gd?PO₄?₃.The emission spectra of the products were measured.Concentration quenching of the prepared phosphors was studied based on the Van Uitert model,and it was concluded that the exchange interaction was responsible for energy transfer between Eu³⁺ and leads to the concentration quenching.The temperature dependence of ⁵D₀ fluorescence emissions was analyzed,and it was deduced that the thermal quenching behavior of ⁵D₀ fluorescence followed well the crossover model.Meanwhile,the ⁵D₀?⁷F_J radiative transition rates,fluorescence branching ratios and the J-O parameters were calculated by using the emission spectra and fluorescence decay.?2?The XRD patterns indicated the as-prepared GdNbO₄:Sm³⁺ products are pure phase,and the emission spectra for all the samples were measured under the same experimental conditions.According to the Van Uitert mode the concentration quenching behavior of Sm³⁺ fluorescence was analyzed,and the D-D interaction between Sm³⁺ ions was found to be the main physical mechanism.Finally,the dependence of color coordinates on the Sm³⁺ doping concentration was studied.The results of color coordinates for all the samples showed doping concentration greatly influenced the color coordinates,thus they can be tuned by the RE ion doping concentration.?3?It was confirmed that all the GdNbO₄:Dy³⁺ samples exhibited pure phase by XRD analysis.On the basis of emission spectra of all the samples measured,the dependence of concentration on Dy³⁺ fluorescence emission was studied.The results showed the D-D interaction between Dy³⁺ ions were found to be the main physical mechanism by Van Uitert mode analysis.Meanwhile,temperature dependent intensity ratio of Y/B in the products was calculated,and the relationship between the color coordinates and Dy³⁺ doping concentration indicated the color coordinates can be adjusted and controlled by RE ion doping concentration.