Enhanced red luminescence of Ca3Si2−xMxO7:Eu3+ (M = Al, P) phosphors via partial substitution of Si4+ for applications in white light-emitting diodes

A red-emitting phosphor Ca2.91Si2O7:0.09Eu3+ with partial Al3+/P5+ substitution on Si4+ was synthesized via a simple solid-state method, and the effects of the introduction of the M3+/5+ (M = Al, P) ions on the crystal structure and photoluminescence performance of Ca2.91Si2−xMxO7:0.09Eu3+ 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 Ca3Si2O7 remained the same after the introduction of Al3+ and P5+ ions. The characteristic emission of Eu3+-doped Ca3Si2−xMxO7 phosphors exhibited two main peaks at 617 nm (red) and 593 nm (orange) under excitation at 394 nm, which originated from the 5D0 → 7F2 and 5D0 → 7F1 electron transitions of Eu3+ ions. After the partial substitution of Al3+ and P5+, the red emission intensities of the Ca2.91Si2O7:0.09Eu3+ phosphors were significantly enhanced by 1.88- and 1.42-fold, respectively, which is attributed to the crystal-field effect around Eu3+. Meanwhile, the luminescence intensities of the Ca2.91Si1.96Al0.04O7:0.09Eu3+ and Ca2.91Si1.94P0.06O7:0.09Eu3+ phosphors at 210 °C were 79.36