Enhanced red luminescence of Ca ₃ Si _{2− <i>x</i>} M _<i>x</i> O ₇ :Eu ³⁺ (M = Al, P) phosphors via partial substitution of Si ⁴⁺ for applications in white light‐emitting diodes

Abstract

Abstract A red‐emitting phosphor Ca 2.91 Si 2 O 7 :0.09Eu 3+ with partial Al 3+ /P 5+ substitution on Si 4+ was synthesized via a simple solid‐state method, and the effects of the introduction of the M 3+/5+ (M = Al, P) ions on the crystal structure and photoluminescence performance of Ca 2.91 Si 2− x M x O 7 :0.09Eu 3+ phosphors were investigated. The X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDS), and X‐ray photoelectron spectroscopy (XPS) results revealed that the structure of Ca 3 Si 2 O 7 remained the same after the introduction of Al 3+ and P 5+ ions. The characteristic emission of Eu 3+ ‐doped Ca 3 Si 2− x M x O 7 phosphors exhibited two main peaks at 617 nm (red) and 593 nm (orange) under excitation at 394 nm, which originated from the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 electron transitions of Eu 3+ ions. After the partial substitution of Al 3+ and P 5+ , the red emission intensities of the Ca 2.91 Si 2 O 7 :0.09Eu 3+ phosphors were significantly enhanced by 1.88‐ and 1.42‐fold, respectively, which is attributed to the crystal‐field effect around Eu 3+ . Meanwhile, the luminescence intensities of the Ca 2.91 Si 1.96 Al 0.04 O 7 :0.09Eu 3+ and Ca 2.91 Si 1.94 P 0.06 O 7 :0.09Eu 3+ phosphors at 210 °C were 79.36% and 77.53% of those at 30 °C, respectively, indicating their excellent thermal stability. Moreover, the as‐prepared Ca 2.91 Si 1.96 Al 0.04 O 7 :0.09Eu 3+ and Ca 2.91 Si 1.94 P 0.06 O 7 :0.09Eu 3+ red‐emitting phosphors were combined with a near‐ultraviolet chip of 395 nm to fabricate red‐light‐emitting diode (LED) and white (w)‐LED devices with excellent chromaticity features. In summary, Al 3+ /P 5+ ‐substituted Ca 2.91 Si 2 O 7 :0.09Eu 3+ can serve as red‐emitting phosphors for applications in w‐LEDs.

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