Dual Liquid/Vapor-Fed Flame Synthesis For The Effective Preparation Of Sio2@Yalo3:Nd3+ Nanophosphors

Yttrium aluminum oxide YAlO 3 is an attractive laser host material for lanthanide ions like Nd 3 + . In this paper, a dual liquid/vapor-fed flame synthesis (DLVF) system is developed for investigating the role of SiO 2 coating on flame-made YAlO 3 :Nd 3 + nanophosphors. The hexamethyldisiloxane (HDMSO) vapor is flexibly fed into the YAlO 3 :Nd 3 + flame spray flow at different positions and molar ratios. We find that the introduction of SiO 2 coating dramatically improves the crystallinity of YAlO 3 :Nd 3 + cores because of the heatinsulation effect and nearly doubles the fluorescence intensity. Through a timescale analysis, we demonstrate that the best timing for coating injection is when the small particles have already been formed but not heavily aggregated. An early injection could result in segregated SiO 2 particles and some impurities like Al 2 SiO 5 , while a delayed injection leads to the coating of SiO 2 on the entire aggregates instead of on individual particles. Experiments of different coating ratios show that the coating ratio 1:1 of Si:(Y + Nd) produces the best crystallinity and strongest fluorescence intensity. Further increase of the coating ratio does not show any improvements of the crystallinity, and may even causes the decrease of the relative fraction of Nd 3 + ions. Compared with YAG:Nd 3 + bulk materials (with a typical optimum doping concentration 1.1mol%) and uncoated YAlO 3 :Nd 3 + nanophosphors (with an optimum doping concentration 2 mol%), the SiO 2 coating promotes the optimum Nd 3 + doping concentration up to 3 mol%. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.