Direct synthesis of Sr₃Al₂(OH)₁₂ from solution for preparation of fine-grained Sr₃Al₂O₆ phosphors at low temperature

The precursors Sr₃Al₂(OH)₁₂ can be directly precipitated from solution near room temperature under the normal pressure. The cubic Sr₃Al₂O₆ with fine grain size can be synthesized from Sr₃Al₂(OH)₁₂ at the temperature as low as 600 °C. Especially, the rare earth element, such as Eu³⁺ etc., as luminescent center, has been simultaneously integrated into the lattices of Sr₃Al₂O₆. The luminescent intensities of the samples annealed at a temperature over 800 °C are strong enough for phosphors, and increase with the annealing temperatures, reach a maximum at 1200 °C and then drop down at 1300 °C. The grain sizes of all the samples annealed below 1200 °C are smaller than 1 μm and suitable for mixing with other phosphors in the applications. The photoluminescent spectra of the Sr₃Al₂O₆:Eu³⁺ reveal that the intensities of both emission and excitation peaks increase with the dose of Eu³⁺, and reach maxima at the dose level about 1.2%, then decrease due to concentration quenching. A new excitation band at 230 nm has been observed in heavier doped samples due to the complex point defects produced by association.