Sulfate-Ion Pillared Layered Hydroxide of Eu2(OH)4SO4·nH2O: Controlled Hydrothermal Processing, Thermal Decomposition, and Photoluminescence

Sulfate-ion pillared layered hydroxide of Eu2(OH)4SO4·nH2O (n~2, SO42--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 Eu2O2SO4 in the temperature range of 300-1000 °C while in flowing H2 hexagonal Eu2O2S was resulted in the 600-1000 °C range. Strong red emissions were found at 621 nm for the SO42--LEuH and 627 nm for Eu2O2S under excitation at 396 nm (the 7F0-5L6 transition of Eu3+). Improved luminescence intensity was also observed for the Eu2O2S powder calcined at a higher temperature.