High performance of La-doped Y2O3 transparent ceramics

As an optical material,Y2O3 transparent ceramics are desirable for application as laser host materials.However,it is difficult to sinter and dense of Y2O3 hinders the preparation of high-quality optical ceramics via traditional processes.In this work,we use La2O3 as a sintering aid for fabricating high-transparency Y2O3 ceramics using a vacuum sintering process.It is demonstrated that the in-line optical transmittance of 15.0 at%La-doped Y2O3 at a wavelength of 1100 nm achieves a transmittance of 81.2%.A sintering kinetics analysis reveals that a grain-boundary-diffusion-controlled mechanism dominates the faster densification at high La3+concentrations.It is also shown that both the mechanical and thermal properties of Y2O3 transparent ceramics are significantly improved upon the increase of La2O3 sintering additives.The results indicate that a La-doped Y2O3 transparent ceramic is a promising candidate for a laser host material.

Investigation of emission properties of Tm^(3+) :Y_2O_3 transparent ceramic

A transparent and emitting ceramic of Y203 doped with 6% Tm3＋ ions is fabricated by vacuum sintering with ZrO2. Absorption, photoluminescence （PL）, and PL excitation （PLE） spectra are investigated in a spectral range of 200 to 2 100 nm at various temperatures between 296 and 12 K. Intense emission band appears at 450 to 465 nm in the visible range. Near-infrared emission bands are observed at 1 200 to 1 300 nm and 1400 to 1 550 nm, with intense peaks at 1270, 1450, and 1 523 nm. The luminescence mechanisms and potential applications of the emissions are discussed with the help of Judd-Ofelt theory and PLE spectra.

High-entropy(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3:A promising thermal/environmental barrier material for oxide/oxide composites

Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 ceramic matrix composites(CMCs)from the corrosion of high-temperature water vapor in combustion environments.Nevertheless,the relatively high thermal conductivity is a notable drawback of YAl O3 for environmental barrier coating application.Herein,in order to make REAl O3 more thermal insulating,a novel high-entropy rare-earth aluminate ceramic(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized.The as-prepared(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient(9.02×10-6/oC measured from room temperature to 1200℃)to that of Al2 O3.The thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 at room temperature is 4.1 W·m-1K-1,which is almost one third of the value of YAl O3.Furthermore,to effectively prevent the penetration of water vapor from possible pores/cracks of coating layer,which are often observed in T/EBCs,a tri-layer EBC system REAl O3/RE3 Al5 O12/(Al2 O3 f/Al2 O3 CMCs)is designed.Close thermal expansion coefficient to Al2 O3 and low thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3,as well as the formation of dense garnet layer at(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2 O3 interface,indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al2 O3 f/Al2 O3 CMCs.