Synthesis of a Solid Solution Series of Layered EuxGd1−x(OH)2.5Cl0.5·0.9H2O and Its Transformation into (EuxGd1−x)2O3 with Enhanced Photoluminescence Properties

The synthesis of a series of new layered rare-earth hydroxide solid solutions and their transformation into (Eu(x)Gd(1-x))(2)O(3) crystallites are described. Highly crystalline platelets of Eu(x)Gd(1-x)(OH)(2.5)Cl(0.5) x 0.9 H(2)O solid solutions with various Eu(3+)/Gd(3+) ratios were prepared through a homogeneous precipitation method. The hydroxide solid-solution samples exhibited characteristic Eu(3+) photoluminescence properties through the energy transfer from Gd(3+) to Eu(3+) and the self-excitation of Eu(3+). Cubic (Eu(x)Gd(1-x))(2)O(3) crystallites were obtained via quasi-topotactic transformation of Eu(x)Gd(1-x)(OH)(2.5)Cl(0.5) x 0.9 H(2)O solid solutions above 800 degrees C. The as-transformed cubic (Eu(x)Gd(1-x))(2)O(3) crystallites well retained the original platelet morphology and single crystalline nature, and exhibited greatly enhanced photoluminescence properties with respect to the precursor hydroxides. The Eu(3+) content of 0.05 in the cubic (Eu(x)Gd(1-x))(2)O(3) gave a maximum luminescence intensity, which is comparable with that of a commercial Y(2)O(3):Eu phosphor.