Enhanced local symmetry achieved zero-thermal-quenching luminescence characteristic in the Ca2InSbO6:Sm3+ phosphors for w-LEDs

A material’s structure vitally affects its luminescence property, which in turn determines its application. Therefore, understanding the correspondence between structural local symmetry and luminescence characteristics is vital for the design and synthesis of optical materials. A series of solid solution reddish-orange-emitting phosphors Ca2InSbO6:Sm3+ (CISO:Sm3+) was synthesized by the high-temperature solid-phase method and applied for white-light-emitting diodes (w-LEDs). Under 407 nm excitation, CISO:Sm3+ phosphors showed intense reddish-orange emission at 600 nm that is attributed to the 4G5/2 → 6H7/2 transition of Sm3+ ions. Given that Sm3+ ions are a structural probe, the relationship between their local symmetry and luminescence properties was discussed in detail. The photoluminescence intensity of CISO:Sm3+ phosphors continuously increases with rising temperature from 298 to 480 K based on the enhanced local symmetry. This phenomenon was further analyzed using the trap theory and charge compensation mechanism. High color purity (~99.9%) and proper Commission International del′Eclairage (CIE) chromaticity coordinates were achieved for the CISO:Sm3+ phosphors. Finally, the fabricated w-LED displayed superior color rendering index (Ra = 93) and CIE chromaticity coordinates (0.330, 0.357) and thus has great potential as reddish-orange-emitting substitutes in horticultural and solid lighting. This work initiates a new insight to construct thermally stable phosphors for optical applications.