Effects of Gd3+Substitution on the Fabrication of Transparent (Y1-xGdx)3Al5O12 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 Gd3+-substituted transparent (Y1-xGdx)(3)Al5O12 (x=0.01, 0.5, 0.75, and 1) ceramics via solid reactive sintering has been investigated. The effects of Gd3+ 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 Gd3+ substitution favors the formation of kinetically stable intermediate compounds, particularly REAlO3 (RE=Y+Gd), and thus retards the crystallization of an RE3Al5O12 garnet. The samples of x=1 composition cracked upon vacuum sintering at temperatures above 1600 degrees C, mainly due to the volumetric expansion induced by garnet formation. The transparent Y1.48Gd1.5Ce0.02Al5O12 ceramic (inline transmittance: similar to 65% at 800 nm) vacuum sintered at 1700 degrees C shows an emission band peaked at similar to 570 nm upon UV excitation at 340 nm, exhibiting a red-shift by similar to 40 nm in comparison with the regular emission from YAG:Ce.