The zero-phonon line (ZPL) of Mn4+, which highly depends on its local environment, is usually much weaker than the vibrational phonon sidebands. In this work, an ultraintense ZPL emission, coming from a brand new red-emitting Rb2LiGaF6:Mn4+ (RLGFM) phosphor upon blue light excitation, is presented. The interesting spectral characteristic originates from the nonequivalent substitution of Mn4+ for Ga3+ in a rigid octahedral structure with a low symmetry, which induces neighboring cation vacancies that distort the local symmetry of the [MnF6] octahedra. Benefiting from the ultraintense ZPL emission, a wide color gamut is achieved using RLGFM and β-SiAlON:Eu2+ as color converters. Moreover, a comprehensive investigation on the thermal quenching behavior is also conducted to provide detailed insights to explore novel Mn4+ red phosphors for high-quality backlight display applications.

The red Cs2NaAl3F12:Mn4+ phosphor with intense ZPL emission was obtained via the occupation of Mn4+ for Al3+, indicating its high colour purity and potential use in WLEDs.

A novel red-emitting Rb2KGaF6:Mn4+ phosphor with octahedral particulate morphology was presented. The XRD Rietveld refinement results indicate that the phosphor crystallized into the cubic phase of Fm 3 ¯ m space group with double perovskite structure. The photo-luminescence spectrum exhibits intense red emission lines with zero-phonon line (ZPL) and v 6 peak locating at 620 and 628 nm respectively. The optical parameters of low color temperature (T c = 3824 K) and high color rendering index (R a = 90.2 ) from white LED imply its potential application in solid-state lighting.