Preparation And Luminescence Properties Of Ba₃Y₂（BO₃）₄ Phosphors Doped With Rare Earth

White-light LEDs are extensively used in lighting and display due to their merits such as energy-saving,long lifetime,high efficiency,and quick response.The commonly employed method to produce white-light LEDs is the phosphor conversion technique.As an essential component,the phosphor significantly impacts the performance of white-light LEDs.Borate phosphors are a promising class of phosphor substrates,valued for their eco-friendliness,simple synthesis process,low sintering temperature,high luminosity,variety,and good structural rigidity.In this paper,we prepare phosphors suitable for white-light LEDs using Ba₃Y₂（BO₃）₄ as the substrate,doped with different rare-earth ions,and study the crystal structure,luminescent properties,thermal quenching,and fluorescence lifetime of the samples.The specifics are as follows:1.High brightness,thermally stable pure phase green Ba₃Y₂（BO₃）₄:x Tb³⁺phosphors were synthesized through high-temperature solid-phase method.XRD spectra indicate that the doping of Tb³⁺ions did not cause a change in the crystal structure,resulting in pure phase samples.Spectral analysis of the sample revealed broad absorption between 200 nm-300 nm,attributed to the 4f→5d transitions of Tb³⁺,while the excitation peaks between 300 nm-500 nm belong to the f-f transitions of Tb³⁺.The emission spectra of the sample lies within the 450 nm-650 nm range,with emission peaks at 490nm（⁵D₄-⁷F₆）,545nm（⁵D₄-⁷F₅）,585nm（⁵D₄-⁷F₄）,624nm（⁵D₄-⁷F₃）,all characteristic of Tb³⁺,with the highest intensity at around 545nm.The optimum doping concentration of Tb³⁺ions is x=1.5,with the quenching mechanism attributed to energy transfer between neighboring ions.The longest fluorescence lifetime of the sample,2.38 ms,was observed when x=0.75.At a temperature of 433K,the luminosity of the sample is 106.2%of its room temperature value,indicating good thermal stability.The LED color coordinates of the Ba₃Y₂（BO₃）₄:Tb³⁺combined with commercial phosphor packaging are（0.41,0.37）,with the LED sample having a low color temperature（3232 K）and high color rendering index（90.1）.2.A novel pure phase blue Ba₃Y₂（BO₃）₄:x Ce³⁺phosphors were synthesized using the high-temperature solid-phase method.XRD spectra indicate the samples are of pure phase.Luminescence analysis reveals a broad emission peak between 375nm-650 nm under 360 nm excitation,with the peak center near 420 nm(5d-4f transitions of Ce³⁺ions).The optimum doping concentration of Ce³⁺ions is x=0.06,and the quenching mechanism is the electric multipole interaction.The longest fluorescence lifetime,21.06 ns,was observed when x=0.02.At a temperature of 423K,the luminosity of the sample is 41%of its room temperature value,indicating room for improving the thermal stability.The LED color coordinates of the Ba₃Y₂（BO₃）₄:Ce³⁺combined with commercial phosphor packaging are（0.36,0.38）,with the LED sample having a relatively low color temperature（4680 K）and a high color rendering index（86.6）.3.A series of orange Ba₃Y₂（BO₃）₄:x Sm³⁺phosphors were synthesized using the high-temperature solid-phase method.Luminescent characteristics of Ba₃Y₂（BO₃）₄:Sm³⁺phosphor were studied.XRD spectra indicate the samples are of pure phase.The emission spectrum of this phosphor lies between 500 nm-680 nm,with peak emission wavelengths at 565 nm,602 nm,and 650 nm,attributed to the transitions of Sm³⁺at⁴G_5/2→⁶H_5/2,⁴G_5/2→⁶H_7/2,and ⁴G_5/2→⁶H_9/2 levels respectively.The optimum doping concentration is x=0.06,and the quenching mechanism is attributed to electric dipole-dipole interaction.With increasing doping concentration of Sm³⁺ions,the CIE coordinates of the samples shift from（0.58,0.42）to（0.59,0.41）,all within the orange light zone,indicating good color stability.4.A series of white Ba₃Y₂（BO₃）₄:x Dy³⁺phosphors were synthesized using the high-temperature solid-phase method.Luminescent characteristics of Ba₃Y₂（BO₃）₄:x Dy³⁺phosphor were studied.XRD spectra indicate the samples are of pure phase.The emission spectrum of this phosphor lies between 450 nm-650 nm,with peak emission wavelengths at 485 nm and 578 nm,attributed to the transitions of Dy³⁺at⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 levels respectively.The optimum doping concentration is x=0.06,and the quenching mechanism is attributed to electric dipole-dipole interaction.With increasing doping concentration of Dy³⁺ions,the CIE coordinates of the samples shift from（0.34,0.38）to（0.35,0.38）,all within the white light zone,indicating good color stability.5.A series of green Ba₃Y₂（BO₃）₄:1.5Tb³⁺x Ca²⁺（x=0,0.1,0.3,0.6,0.9,1.2,1.5,1.8,2.1,2.4,2.7,3）phosphors were synthesized through high-temperature solid-phase method,where Ca²⁺ions replaced Ba²⁺ions.XRD spectra show that the samples are of pure phase.With an increase in the replacement concentration of Ca²⁺ions,the luminosity of the phosphor initially increases and then decreases,with the replacement concentration of Ca²⁺ions at x=0.1 showing an integrated luminosity intensity of 105%compared to the Ba₃Y₂（BO₃）₄:1.5Tb³⁺sample.The optimal replacement concentration of Ca²⁺ions is x=0.1.Results indicate that the brightness of Ba₃Y₂（BO₃）₄:1.5Tb³⁺phosphor can be improved with an appropriate replacement of Ba²⁺with Ca²⁺ions.