New red-emitting phosphors KLiSnF6:xMn4+ (KLSFM, x = 4%, 6%, 8%, 10%, and 12%) for LED lighting were synthesized by an ion-exchange method at room temperature. Among these phosphors, the KLSFM (8 mol%) sample exhibits the strongest excitation in the blue region and emission in the red region. The corresponding translucent fluorescent sheet prepared by the pressure method shows similar luminescent properties which are identical to the powders with the strongest absorption at 467 nm and narrow emission around 632 nm. The fluorescent sheet offers high transmittance in UV–Vis region (close to 100% beyond 550 nm) and better thermal stability and color stability. For comparison, the white pc-LEDs based on the KLSFM (8 mol%) phosphor and fluorescent sheet all emit intense white light with an ideal color rendering index (CRI >93) and a good correlated color temperature (CCT <3500 K). However, the white pc-LED based on the fluorescent sheet have more advantage in application for high-power devices. Working at 200 mA, the LED fabricated with the translucent sheet still keeps excellent performance with a high CRI of 90.1 and a low CCT of 3874 K. The working temperature for this device is only 90 °C after working for 40 min, which is lower than that of the device with the KLSFM (8 mol%) powder, furtherly proving that the translucent sheet has excellent heat dispersion. Therefore, the KLSFM (8 mol%) translucent sheet could be used for high-power pc-LEDs as a red component.
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