Dual-Mode Luminescence with Broad Near UV and Blue Excitation Band from Sr₂CaMoO₆:Sm³⁺ Phosphor for White LEDs

Dual-mode excitation properties were introduced in Sm³⁺ doped Sr₂CaMoO₆ prepared by a high temperature solid state reaction technique. Two ways are available to generate white light in the single-component phosphor activated by Sm³⁺ ions. Warm white light can be obtained from Sr_1.995Sm_0.005CaMoO₆ phosphor pumped by 380 or 411 nm excitation energy. The full visible spectral emission of the single-phase phosphor comes from the high and low level emission lines of Sm³⁺ ions as well as the intrinsic luminescence of MoO₆ group. It is also competitive as yellow-emitting phosphor for blue pumped white LEDs and gives three emission bands at 567, 603, and 650 nm, presenting yellow luminescence upon 466 nm radiation. The 650 nm red emission band corresponding to ⁴G_5/2 → ⁶H_9/2 transition of Sm³⁺ can make its color rendering index better. The excellent photoluminescence of Sr₂CaMoO₆ is related to the partial tilting CaO₆ octahedral and the lowered symmetry were confirmed by General Structure Analysis System. Band gap of Sr₂CaMoO₆ estimated from the diffuse reflection spectra and also calculated by CASTEP mode shows its semiconducting character. All the results show that the Sr_2-xSm_xCaMoO₆ phosphors have considerable potential for applications in near UV LED or pumped by blue LED chip.