Borate-based luminescent materials: A comprehensive review of structural influences on thermal stability and luminescence characteristics

Abstract

Borate phosphors, with a rich developmental history spanning nearly a century have become indispensable in solid-state lighting. This review systematically classifies borate phosphors based on composition, crystal structure, and luminescence properties, encompassing rare earth, alkaline earth, and transition metal-doped variants, as well as single-phase, multiphase, orthoborate, and metaborate systems. A central focus is the intricate correlation between the host's coordination chemistry and the material's luminescent behavior. The fundamental mechanisms governing luminescence, such as basic f-f and d-f transitions, crystal field splitting, the nephelauxetic effect, energy transfer processes, and concentration quenching, are comprehensively discussed, alongside lattice dynamics and phonon interactions. The inherent robust nature of borate anionic groups, integrated into stable crystal lattices, is highlighted. We also reviewed recent breakthroughs in the field, presenting a new generation of sophisticated borates. Understanding this intricate structure-property relationship is paramount for the rational design of next-generation borate phosphors for advanced photonic applications.