Dual‑functional application of Ca_(2)Ta_(2)O_(7):Bi^(3+)/Eu^(3+)phosphors in multicolor tunable optical thermometry and WLED

A series of Bi^(3+)/Eu^(3+)co-doped Ca_(2)Ta_(2)O_(7)(CTO:Bi^(3+)/Eu^(3+))phosphors were prepared by high-temperature solid-state method for dual-emission center optical thermometers and white light-emitting diode(WLED)device.By modulating the doping ratio of Bi^(3+)/Eu^(3+)and utilizing the energy transfer from Bi^(3+)to Eu^(3+),the tunable color emission ranging from green to reddish-orange was realized.The designed CTO:0.04Bi^(3+)/Eu^(3+)optical thermometers exhibit signifcant thermochromism,superior stability,and repeatability,with maximum sensitivities of Sa=0.055 K^(−1)(at 510 K)and Sr=1.298%K^(−1)(at 480 K)within the temperature range of 300−510 K,owing to the diferent thermal quenching behaviors between Bi^(3+)and Eu^(3+)ions.These features indicate the potential application prospects of the prepared samples in visualized thermometer or hightemperature safety marking.Furthermore,leveraging the excellent zero-thermal-quenching performance,outstanding acid/alkali resistance,and color stability of CTO:0.04Bi^(3+)/0.16Eu^(3+)phosphor,a WLED device with a high Ra value of 95.3 has been realized through its combination with commercially available blue and green phosphors,thereby demonstrating the potential application of CTO:0.04Bi^(3+)/0.16Eu^(3+)in near-UV pumped WLED devices.

Development of a novel Eu^(3+)-doped tantalate red-emitting phosphor for w-LEDs application

Two novel phosphors LiBa_(4(1-x))Eu_(4x)Ta_(3)O_(12)(H-LBTO:xEu^(3+)) and Li_(0.25)Ba_(1-x)Eu_(x)Ta_(0.75)O_(3)(C-LBTO:xEu^(3+))were prepared successfully by a molten salt method.The transformation between these two structures was realized by changing the sintering temperature or changing the Eu^(3+) ions concentration,which was also demonstrated by the X-ray diffraction(XRD),scanning electron microscopy(SEM),diffuse reflectance spectra(DRS),and photoluminescence excitation(PLE) analyses,Both the sintering temperature and the Eu^(3+)ions doping concentration have significant impact on the formation of the crystal phase.All these phosphors sintered at 1023 K exhibit two major luminescence lines at 594 and 614 nm under nearUV light of 395 nm excitation,corresponding to Eu^(3+)ions typical transitions of ^(5)D_(0)→^(7)F_(1) and ^(5)D_(0)→^(7)F_(2).The optimum concentration of Eu^(3+) ions is 9 mol% for C-LBTO:xEu^(3+) samples and the quenching interaction type is the nearest-neighbor ion interaction.The thermal stability of the C-LBTO:0.09Eu^(3+)sample was investigated in detail and the device application further suggests that C-LBTO:0.09Eu^(3+) can be used as a red phosphor for near-UV excited w-LEDs in lighting.

Development of red phosphor Li_(8)CaLa_(2)Ta_(2)O_(13):Eu^(3+)for WLEDs and anti-counterfeiting applications

A set of novel red phosphors Li_(8)CaLa_(2)Ta_(2)O_(13):Eu^(3+)(LCLTO:xEu^(3+))were successfully prepared using a solid-state reaction method.The properties of the prepared samples,including phase purity,elemental composition,and morphology,were systematically investigated using X-ray diffraction,scanning electron microscopy,and diffuse reflectance spectroscopy analyses.The 610 nm maximum emission peak is attributed to the^(5)D_(0)→^(7)F_(2)transition of Eu^(3+)ion under 394 nm irradiation.Among all the LCLTO:xEu^(3+)phosphors,LCLTO:0.6Eu^(3+)showed the strongest emission intensity because of the concentration quenching effect of the electric dipole-dipole in-teraction among the Eu^(3+)ions,which was also demonstrated by the decay curves.Remarkably,the emission intensity of the optimal LCLTO:0.6Eu^(3+)phosphor,which exhibited a high internal quantum efficiency of 49.30%and excellent color purity of 96.79%,was approximately 2.29 times higher than that of commercial Y203:Eu^(3+)red phosphors.The thermal stability of the LCLTO:0.6Eu^(3+)sample with good color stability was meticulously inves-tigated.The fabricated white-light-emitting diode(WLED)exhibited a superior color-rendering index of Ra=82 and chromaticity coordinates of(0.3260,0.3639),suggesting that LCLTO:0.6Eu^(3+)has potential applicability in developing efficient and high-quality WLEDs.Moreover,the prepared LCLTO:0.6Eu^(3+)/PDMS composite film demonstrated exceptional flexural resistance and chemical stability,indicating considerable promise for practical anti-counterfeitingapplications.