Stabilization of Fluorescent [Ag_m]ⁿ⁺ Quantum Clusters in Multiphase Inorganic Glass-Ceramics for White LEDs

Silver quantum clusters ([Agm]n+ QCs) are a type of efficient broadband fluorescence centers with m and n related quantum size effects but usually lack chemical and thermal stability. To solve such a problem and exploit [Agm]n+ QCs potential applications in white LED lighting, [Agm]n+ QCs and rare earth ions (RE3+) were designed to be selectively enriched into B2O3-rich spinodal nanophase separation and SrF2 nanocrystals in fluoroborosilicate multiphase glass-ceramics. In this work, Ag/RE3+-codoped glasses and glass-ceramics with a designed composition were prepared through a melt-quenching method and subsequent heat treatment. The B2O3-rich spinodal nanophase separation and SrF2 nanocrystals were stepwise formed in these glass-ceramics. Taking Ag/Er3+-codoped glass-ceramics for an example, the special microstructures were clearly revealed by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDX) mappings. By the strategies of controlling [Ag+] solubility and charge compensating to [AlO4]−, [BO4]−, and [ZnO4]2– tetrahedra, a large quantity of [Agm]n+ QCs were stabilized in the glass networks with regulated m and n. By the strategies of RE3+/Al3+ and Ag+/Na+ competitive distribution, the solubility of Ag+ in B2O3-rich glassy phases was effectively increased, and [Agm]n+ QCs were eventually stabilized to withstand the postcrystallization procedures at high temperatures up to 650 °C. By the multiphase strategy, Ag and RE3+ were selectively partitioned into the B2O3-rich nanosize glassy phases and SrF2 nanocrystals, respectively. Thus, energy transfers (ETs) between [Agm]n+ and RE3+ can be well-suppressed to enhance the photoluminescence quantum yields (PL QYs) of the multiphase glass-ceramics. Those engaged [Agm]n+ with largely improved white light-emitting diode (WLED) performances, e.g., QY and color rendering index (CRI), in the glass-ceramics. This suggests that Ag/RE3+-codoped glass-ceramics can be ideal candidate phosphors for high-power WLED lighting devices.