Reactive SPS of Al₂O₃–RE:YAG (RE = Ce; Ce+Gd) composite ceramic phosphors

Abstract

Ultrafine-grained Al2O3−RE:YAG (RE=Ce; Ce+Gd) composite ceramics were obtained for the first time by reactive SPS using commercially available initial oxide powders. The effect of key sintering parameters (temperature and dwell time, external pressure) on densification peculiarities, structural-phase state, and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown. Parameters of reactive SPS at which there is partial melting with the formation of near-eutectic zones of the Al2O3−YAG system/coexistence of several variations of the YAG-type phase were established. Pure corundum-garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425°C / 30 min / 30-60 MPa. The external quantum efficiency of the phosphor converters reached 80.7% and 72% with close lifetimes of ~63.8 nsec, similarly to commercial Ce:YAG materials, which is promising for further application in the field of high-power white LEDs and LDs.

Recent Advances in Preparing Transparent Phosphor Ceramics for High-Index Color Rendering and High-Power Lighting

“…For instance, in multi-phase ceramics, taking Al 2 O 3 -YAG:Ce 3+ as an example, it is usually difficult to achieve uniform distribution, which has a negative impact on the heat dissipation and uniformity of the luminescent centers of the ceramics. To address the issue, “unique” microstructures of these phosphor converters were developed to control light scattering and achieve color uniformity [ 84 ]. Homogeneous initial powder materials were obtained by regulating the excess of Al 3+ of YAG:Ce 3+ in the process of co-precipitation, which provided a possible way to optimize the composition uniformity of Al 2 O 3 -YAG:Ce 3+ TPCs [ 85 ].…”

Simplified Single‐Step Fabrication of Composite Transparent Ceramics

“…[3] Spark plasma sintering (SPS), also commonly referred to as field-assisted sintering technology, is a rapid single-step densification technique [21] that keeps growing in popularity while being extended toward more advanced materials. [22] Regarding transparent ceramics, SPS has been successfully used to fabricate various laser ceramics, such as Nd 3þ :Lu 2 O 3 , [23] Yb 3þ :Y 2 O 3 , [24] Er: 3þ YAG, [25] and Nd 3þ :YAG [26] as well as ceramic phosphors such as Ce 3þ YAG, [27] Al 2 O 3 -Ce 3þ ,Gd 3þ :YAG, [28] and Mn 2þ : MgAl 2 O 4 . [29] Herein, we demonstrate a versatile single-step fabrication method of transparent ceramic composites by SPS.…”

Microstructure and Mechanical Characterization of Novel Al2O3–(NiAl–Al2O3) Composites Fabricated via Pulse Plasma Sintering

“…Advanced sintering techniques are also used. Among them are reactive hot pressing (RHP) [30], self-propagating high temperature synthesis (SHS) [31], combustion synthesis (CS) [32], spark plasma sintering (SPS) [33,34], and pulse plasma sintering (PPS) [35][36][37]. Different methods have various influences on the formation of multiphase composite materials.…”