Lutetium(III) sulfide, also known as lutetium sesquisulfide, is an inorganic compound of lutetium and sulfur with the chemical formula Lu2S3. It is one of the binary sulfides of lutetium.
Structure and properties At ambient pressure, lutetium(III) sulfide commonly adopts the ε-Lu2S3 structure, which is rhombohedral and isostructural with corundum, α-Al2O3. It crystallizes in space group Rc (No. 167).
Lu2S3 is a high-melting rare-earth sesquisulfide, melting at approximately 1755 °C. It is non-hygroscopic and is stable on exposure to ambient air at room temperature.
Several polymorphs of Lu2S3 are known. Under high pressure and high temperature, a cubic γ-phase with the Th3P4-type structure can be obtained. This phase crystallizes in space group I3d.
Preparation Lutetium(III) sulfide can be prepared by direct reaction of lutetium with sulfur at high temperature under an inert atmosphere:
2 Lu + 3 S → Lu2S3
Single crystals of ε-Lu2S3 have also been grown from the melt using the micro-pulling-down method under high-purity argon. Because of the high melting point and sensitivity of the molten material to oxygen, growth is carried out in a closed, inert system.
High-pressure synthesis can be used to obtain the γ-Lu2S3 polymorph. Single-phase γ-Lu2S3 has been prepared using multi-anvil high-pressure and high-temperature techniques.
Applications Rare-earth sesquisulfides have been investigated for optical and scintillation applications because of their high refractive indices and broad optical transmission ranges.
Cerium-doped Lu2S3 has been studied as a red-emitting scintillator. Lu2S3:Ce3+ crystals have been reported to emit between approximately 550 and 700 nm, with a maximum near 592 nm and a decay time of about 32 ns.
More recently, praseodymium-doped Lu2S3 single crystals have been investigated for luminescence and scintillation applications. Fast Pr3+ 5d→4f emission has been observed under both optical and ionizing-radiation excitation.
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