Photoluminescence, Non-Reduction and Thermal Stability Characteristics of Red Phosphors Ca₃La_3(1-x)Eu_3x(BO₃)₅Prepared in Reducing Atmosphere

Abstract

A series of Ca3La3(1-x)Eu3x(BO3)5 phosphors were prepared via a solid-state reaction under reducing atmosphere. Rietveld refinements were performed by adopting the powder X-ray diffraction data, which indicates the occupations of Eu3+ on both La3+ and Ca2+ sites with a preferred location on the La3+ site over the Ca2+ site. This kind of phosphors could be excited by UV and blue LED in solid-state lighting technology and the CIE chromaticity coordinates for phosphors CLBO: 0.06Eu3+ (λex = 254 nm) and CLBO: 0.12Eu3+ (λex = 393 nm) are (0.6712, 0.3328) and (0.6685, 0.3287), respectively, which are compliant with the national television system committee (NTSC) standard for red chromaticity. The energy transfer rate between the Eu3+-Eu3+ pairs is weak that proved by the results of the decay process and the efficiency of the Eu3+ 5D0→7F2 emission. The mechanism responsible for the non-reduction of Eu3+ was analyzed, which was determined by two factors: 1) no element of the host matrix can be oxidized and 2), cationic vacancies which can be regarded as the electron donor cannot exist. The temperature dependence study shows thermal quenching behavior is attributed to crossover from the 5D0 excited state of the Eu3+ to the charge transfer state band and these phosphors have good thermal stability.

High quality LED lamps using color-tunable Ce3+-activated yellow-green oxyfluoride solid-solution and Eu3+-doped red borate phosphors

“…The red borate Ca 3 La 3(1Àx) (BO 3 ) 5 :3xEu 3+ phosphors were also prepared by the solid-state reaction, for detail information see the previous work reported by our group. 19 Instrumental methods X-ray diffraction measurements were performed on a D8 Bruker diffractometer employing the Cu K a radiation and a Vantec multigap detector in the 5-1251 2y interval. To achieve a better powder-averaged signal, the sample was rotated during data collection, where the axis is perpendicular to the theta and momentum transfer direction.…”

“…35 The crystal structure of CLBO has been determined previously from X-ray powder data by our group. 19 The occupancies of activator Eu 3+ cations can both enter into Ca 2+ and La 3+ sites since the cationic size of Eu 3+ is smaller than both La 3+ and Ca 2+ while it cannot occupy interstitial or B 3+ sites in the CLBO HL due to the large differences in the ionic radius. Meanwhile, the preferred occupancy of Eu 3+ ions on the La 3+ Fig.…”

2D photonic crystal layer assisted thiosilicate ceramic plate with red‐emitting film for high quality w‐LEDs

“…Light‐emitting‐diodes (LEDs) have been developed almost including the whole spectrum (i.e., ultraviolet, visible and infrared wavelengths) and their use has been extended from solid‐state‐lighting to different displays applications . Doping is the most important and efficient method of endowing hosts with various functions.…”