Effects of Gd 3+ Substitution on the Fabrication of Transparent (Y 1−x Gd x ) 3 Al 5 O 12 Ceramics

Gadolinium has been frequently used in scintillators to enhance the X‐ray stopping power and in phosphors to improve the luminescent properties. In this paper, the fabrication of Gd 3+ ‐substituted transparent (Y 1− x Gd x ) 3 Al 5 O 12 ( x =0.01, 0.5, 0.75, and 1) ceramics via solid reactive sintering has been investigated. The effects of Gd 3+ substitution on the phase evolution of the powder mixture, sintering behavior of the powder compact, and properties of the resultant ceramics were mainly demonstrated. It is shown that Gd 3+ substitution favors the formation of kinetically stable intermediate compounds, particularly REAlO 3 (RE=Y+Gd), and thus retards the crystallization of an RE 3 Al 5 O 12 garnet. The samples of x =1 composition cracked upon vacuum sintering at temperatures above 1600°C, mainly due to the volumetric expansion induced by garnet formation. The transparent Y 1.48 Gd 1.5 Ce 0.02 Al 5 O 12 ceramic (inline transmittance: ∼65% at 800 nm) vacuum sintered at 1700°C shows an emission band peaked at ∼570 nm upon UV excitation at 340 nm, exhibiting a red‐shift by ∼40 nm in comparison with the regular emission from YAG:Ce.