Microwave-assisted hydrothermal synthesis and spectroscopic characteristics of a Lu4Hf3O12:Pr scintillator

Abstract

Exclusively high density of Lu₄Hf₃O₁₂ makes it an attractive host for scintillator materials. This paper presents the versatility of microwave-assisted hydrothermal technology (MAH) to fabricate nanocrystalline Lu₄Hf₃O₁₂:Pr luminescent powder. It is shown that by varying the parameters of the fabrication procedure, changing the composition of the liquid medium and/or using polyethylene glycol, PEG 2000, as a surfactant, the morphology of the powders could be modified. In the presence of PEG, obtaining non-agglomerated particles ∼5 nm in diameter was possible. Sintered ceramics at 1700 °C were fabricated using various powders. Photoluminescence and X-ray excited emission spectra showed the Pr³⁺ emission resulting from 4f → 4f transitions. At room temperature the ³P₀ and ¹D₂ levels contributed roughly equally to the total emission in both the powders and sintered ceramics. The former produced luminescence with a decay time of ∼15 μs while the latter was an order of magnitude slower. At 10 K the emission resulted almost exclusively from the ³P₀ level. In addition, a broad-band blue luminescence was observed at low temperatures. Room temperature radioluminescence (RL) was found to be rather inefficient in both the powders and ceramics.