Low-temperature Synthesis of Eu2+ and Dy3+ Doped Strontium Dialuminate (SrAl4O7: Eu2+, Dy3+) Scintillator Materials

Although single crystals are widely used as scintillator materials, the use of polycrystalline powder ones is being proposed as a low-cost alternative. In this report, the synthesis of single phase, highly crystalline divalent europium and trivalent dysprosium doped strontium dialuminate (SrAl4O7: Eu2+, Dy3+) was investigated by modifying the Pechini process, which can be conducted at much lower temperatures compared to the conventional solid state diffusion process. These modifications were necessary due to strontium being one of the host elements in the crystal lattice. Because Sr has a high oxygen affinity, the conventional Pechini process promoted the formation of SrCO3, which hindered the material’s ability to form single phase and highly crystalline SrAl4O7. These are the key requirements for the material, when doped with Eu2+, Dy3+, to serve as a model system for studying the luminescence mechanisms. TG/DTA, XRD, and STEM characterizations were used to explore the region of phase stability of doped dialuminate in the SrO-Al2O3 system, between 700-1300°C. The reduction atmosphere and time were carefully controlled in order to achieve fully reduced samples. Oxygen content analysis performed on the samples revealed interesting reduction behavior in the strontium dialuminates not previously reported in the literature. When unreduced, crystalline, doped strontium dialuminate contained 60% oxygen, while after reduction for 4 hours, this amount decreased to and remained at 35%, independent of the reduction time. However, the glow intensity continued to increase in proportion to the change in the reduction time. The luminescence behavior of these compounds would also be presented in order to investigate the evolving electronic structure in the doped dialuminate