Reliability of fluoride phosphor K 2 XF 6 :Mn 4+ (K 2 SiF 6 :Mn 4+ , K 2 (Si,Ge)F 6 :Mn 4+ , K 2 TiF 6 :Mn 4+ ) for LED application

The red fluoride phosphor K 2 XF 6 :Mn 4+ was prepared by co-precipitation with partial HF in placed with glacial acetic acid. The phase structures and photoluminescence (PL) properties of the red fluoride phosphor K 2 XF 6 :Mn 4+ phosphor have been investigated in detail. Reliability test show that the relative PL intensity of KSFM, K(S,G)FM and KTFM decreased by 14.95%, 18.22% and 67.21% after the ambient condition of high temperature and high humidity (85 °C/RH 85%) for the exposure time of 168 h. The thermal cycling testing results show that the relative PL intensity of KSFM, K(S,G)FM and KTFM decreased by 0.41%, 5.55% and 1.14% after storing the phosphors into an ambient condition of 120 °C for 1 h and − 40 °C for 1 h by turns for five times. The relative PL intensity of KSFM, K(S,G)FM and KTFM decreased by 89.09%, 91.93% and 99.94% after soaking into boiled water for 3 h. It can be summarized that KSFM has the best reliability and KTFM has the worst reliability. Then by mixing the YAG:Ce 3+ and KXFM phosphor and commercial green phosphor with appropriate proportion of the components, it can be found that the luminous efficacy of K 2 XF 6 :Mn 4+ (KSFM, K(S,G)FM, KTFM) after 85°C/RH 85% decreased by 0.14%, 0.54% and 1.06%, after thermal cycling decreased by 2.60%, 1.53% and 3.17% and after hydrolysis decreased by 14.49%, 9.65% and 47.66%. The KTFM after hydrolysis and YAG:Ce 3+ encapsulated WLEDs have the most reduced luminous efficacy. Moreover, the luminous efficacy of K(S,G)FM after hydrolysis and YAG:Ce 3+ encapsulated WLEDs is better than KSFM after hydrolysis and YAG:Ce 3+ encapsulated WLEDs.