Sulfate-ion Pillared Layered Hydroxide of Eu_2(OH)_4SO_4-nH_2O: Controlled Hydrothermal Processing, Thermal Decomposition, and Photoluminescence

摘要

Sulfate-ion pillared layered hydroxide of Eu_2(OH)_4SO_4-nH_2O (n~2, SO_4~--LEuH) was synthesized through controlled hydrothermal reaction, and the phase evolution of which upon calcination in the air and hydrogen was studied in detail. It was found that annealing in the air produced orthorhombic Eu_2O_2SO_4 in the temperature range of 300-1000°C while in flowing H_2 hexagonal Eu_2O_2S was resulted in the 600-1000°C range. Strong red emissions were found at 621 nm for the SO_4~(2-)-LEuH and 627 nm for Eu_2O_2S under excitation at 396 nm (the ~7F_0-~5L_6 transition of Eu~(3+)). Improved luminescence intensity was also observed for the Eu_2O_2S powder calcined at a higher temperature.