Renping Cao,Zhiyi Huang,Bang Lan,Lan Li,Xuehua Yi,Zhiyang Luo,Chenxing Liao,Jing Wang
Ca 3 Zn 3 Te 2 O 12 :Bi 3+ , Ca 3 Zn 3 Te 2 O 12 :Eu 3+ , Ca 3 Zn 3 Te 2 O 12 :Eu 3+ /Bi 3+ are prepared successfully in air. The crystal phase, microscopic image, and optical properties of samples are investigated by the X-ray difractometer, scanning electron microscopy, and edinburgh steady-state FLS 980 spectrograph. The green emission of Ca 3 Zn 3 Te 2 O 12 :Bi 3+ phosphor with excitation at 314 nm is observed and its broad emission spectrum in the range of 360 - 790 nm is attributed to the 3 P 1 → 1 S 0 transition of Bi 3+ ion. Under excitation at 395 nm, the red emission of Ca 3 Zn 3 Te 2 O 12 :Eu 3+ is found, the chromaticity coordinates are (0.6392, 0.3605), and its PL spectrum is in the rang of 575 - 750 nm because of the 5 D 0 → 7 F 0 , 7 F 1 , 7 F 2 , 7 F 3 , and 7 F 4 transations of Eu 3+ ion. The doping Bi 3+ ion can affect the luminescence properties of Ca 3 Zn 3 Te 2 O 12 :Eu 3+ phosphor. The adjustable color light from green to yellow of Ca 3 Zn 3 Te 2 O 12 :Eu 3+ , Bi 3+ phosphor with excitation at 314 nm is revealed when Eu 3+ concentration is changed from 0 to 12 mol%. When the excitation wavelength is 395 nm, Ca 3 Zn 3 Te 2 O 12 :Eu 3+ , Bi 3+ phosphor only emits red light with emission spectrum in the rang of 575 - 750 nm. The energy level diagrams of Eu 3+ and Bi 3+ in Ca 3 Zn 3 Te 2 O 12 :Eu 3+ , Bi 3+ are drawn, which is used to analyze the luminous mechanism of samples.
Research into red phosphors with a high color rendering index is particularly compelling, given the absence of a red component in the spectrum of commercial pc-WLEDs, which combine blue LED chips with yellow-emitting YAG:Ce3+ phosphors. Herein, we reported a novel Eu3+ activated Ca3Zn3Te2O12 red-emitting phosphor, synthesized using a conventional high-temperature solid-phase method. The phase and crystal structures were analyzed by powder X-ray diffraction and Rietveld refinement. The optimal excitation peak of the Ca3Zn3Te2O12:Eu3+ phosphor was located at 395 nm, matching those of conventional commercial near-ultraviolet chips. In addition, the Ca3Zn3Te2O12:9%Eu3+ phosphor exhibited good thermal stability, with an activation energy of 0.267 eV, and the CIE color coordinates hardly changed with temperature. Ultimatel, a high-quality white LED device was fabricated by combining Ca3Zn3Te2O12:9%Eu3+ red phosphor, a commercial BaMgAl10O17:Eu2+ blue phosphor, and(Ba,Sr)2SiO4:Eu2+ green phosphor with a 395 nm near-UV chip. Despite a substantial increase in the input current from 20 to 320 mA, the white-LED maintained a stable color rendering index of around 80, highlighting its consistent performance. These results indicated that Eu3+ activated Ca3Zn3Te2O12 phosphors are promising red emission candidates for white LEDs pumped by near ultraviolet chips.
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