Mn 4 þ -activated fluoride compounds, as an alternative to commercial (oxy)nitride phosphors, are emerging as a new class of non-rare-earth red phosphors for high-efficacy warm white LEDs. Currently, it remains a challenge to synthesize these phosphors with high photoluminescence quantum yields through a convenient chemical route. Herein we propose a general but convenient strategy based on efficient cation exchange reaction, which had been originally regarded only effective in synthesizing nano-sized materials before, for the synthesis of Mn 4 þ -activated fluoride microcrystals such as K 2 TiF 6 , K 2 SiF 6 , NaGdF 4 and NaYF 4 . Particularly we achieve a photoluminescence quantum yield as high as 98% for K 2 TiF 6 :Mn 4 þ . By employing it as red phosphor, we fabricate a high-performance white LED with low correlated colour temperature (3,556 K), high-colour-rendering index (R a ¼ 81) and luminous efficacy of 116 lm W À 1 . These findings show great promise of K 2 TiF 6 :Mn 4 þ as a commercial red phosphor in warm white LEDs, and open up new avenues for the exploration of novel non-rare-earth red emitting phosphors.

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