Effectively enhanced the luminescent properties and water resistance of K2TaF7: Mn4+ red phosphors by introducing In3+ ions in the matrix and constructing a homogeneous core-shell structure

Shell-free K ₂Ta _1-xIn _xF ₇: Mn ⁴⁺ red phosphor was synthesized by introducing In ³⁺ ions in K ₂TaF ₇: Mn ⁴⁺ with a non-centrosymmetric octahedral structure. The strategy of the heterogeneous substitution of In ³⁺ by Ta ⁵⁺ further distorted the octahedral structure, effectively enhanced the emission intensity of Mn ⁴⁺ . Its overall luminous intensity was increased to 6.9 times that of K ₂TaF ₇: Mn ⁴⁺ . Moreover, the red phosphor with a homogeneous core-shell structure was successfully prepared by using a weak reducing agent citric acid to solve the problem of poor water resistance. After soaking in water for 10 days, the emission intensity of the red phosphor with a homogeneous core-shell structure retained 90% of the initial value. It is the first time to successfully construct a core-shell structure for A ₂BF ₇: Mn ⁴⁺ type fluoride phosphors to effectively improve its water resistance. Mixing it with commercial YAG: Ce ³⁺ yellow phosphor and encapsulating them with a commercial blue chip led to the development of warm white light-emitting diodes (WLEDs) with good qualities. K ₂Ta _1-xIn _xF ₇: Mn ⁴⁺ red phosphor with homogeneous core shell is a novel red phosphor with good luminous performances and excellent water resistance.