Optimized photoluminescence of red phosphor Na₂SnF₆:Mn⁴⁺ as red phosphor in the application in “warm” white LEDs

Abstract

The Mn4+ activated fluostannate Na2SnF6 red phosphor was synthesized from starting materials metallic tin shots, NaF, and K2MnF6 in HF solution at room temperature by a two‐step method. The formation mechanism responsible for preparing Na2SnF6:Mn4+ (NSF:Mn) has been investigated. The influences of synthetic parameters: such as concentrations of HF and K2MnF6 in reaction system, reaction time, and temperature on crystallinity, microstructure, and luminescence intensity of NSF:Mn have been investigated based on detailed experimental results. The actual doping concentration of Mn4+ in the NSF:Mn host lattice is less than 0.12 mol%. The most of K2MnF6 is decomposed in HF solution especially in hydrothermal system at elevated temperatures. The color of the as‐prepared NSF:Mn samples changes from orange to white when the temperature is higher than 120°C, which indicates the lower concentration of luminescence centers in the crystals. A series of “warm” white light‐emitting diodes with color rendering index (CRI) higher than 88 and correlated color temperatures between 3146 and 5172 K were obtained by encapsulating the as‐prepared red phosphors NSF:Mn with yellow one Y3Al5O12:Ce3+ (YAG:Ce) on 450 nm blue InGaN chips. The advantage of the synthetic strategy to obtain NSF:Mn can be extended to developing Mn4+‐doped red phosphors from low‐costing metals at room temperature for large‐scale industrial applications.

Rare‐earth‐free Li5La3Ta2O12:Mn4+ deep‐red‐emitting phosphor: Synthesis and photoluminescence properties

“…Up to now, there are two main kinds of hosts for Mn 4+ doping, such as fluorides and oxides. Mn 4+ ‐doped fluorides exhibit line red emission with emission peak at ~630 nm, such as Rb 2 GeF 6 :Mn 4+ , Na 2 SnF 6 :Mn 4+ , K 2 LiGaF 6 :Mn 4+ , BaTiF 6 :Mn 4+ , K 2 NaAlF 6 :Mn 4+ , BaNbOF 5 :Mn 4+ , and (NH 4 ) 3 AlF 6 :Mn 4+ . However, the practical applications of Mn 4+ ‐doped fluorides may be restricted because they are not stable at high temperature or large moisture conditions.…”

Exploration of bluish violet‐emitting phosphor Ca3Al4ZnO10:Ti4+ with enhanced emission by Ca2+ vacancies

“…Nowadays, indoor cultivation has attracted considerable attentions over traditional farming mode due to its distinct merits such as high crop yield and stable growth environment . Artificial lights, such as phosphor‐converted light‐emitting diodes (pc‐LEDs), gas discharge lamps (GDLs), and especially fluorescent lamps, play an important role in this advanced technology . Typically, the absorption area of plant pigments can be subdivided into two parts: the bluish violet and red‐far red lights.…”

Facile synthesis and spectroscopic characterization of siliconitride phosphors for white light‐emitting diodes

“…White light‐emitting diodes (white LEDs) have received attention in recent years as a prospective alternate for usual incandescent and fluorescent light owing to the high brightness, efficiency, low energy consumption, and excellent reliability . The conventional method to generate white light involves the combination of blue InGaN LEDs with yellow‐emitting YAG (Y 3 Al 5 O 12 :Ce 3+ ) phosphors . The conventional white LEDs tend to have high color temperatures (CCT), low thermal stability, and low color‐rendering index (CRI).…”

“…1,2 The conventional method to generate white light involves the combination of blue InGaN LEDs with yellow-emitting YAG (Y 3 Al 5 O 12 :Ce 3+ ) phosphors. 3 The conventional white LEDs tend to have high color temperatures (CCT), low thermal stability, and low colorrendering index (CRI). The inclusion of red phosphors into commercial white LEDs is a proficient approach to improve the performances.…”