High-Pressure Near-Infrared Luminescence Studies of Fe3+-Activated LiGaO2

A Diamond Anvil cell was used for high-pressurestudiesof LiGaO2:Fe powder, emitting light in the near-infraredregion with a 28% quantum efficiency at ambient conditions. The powderis composed of nano-crystallites with average size of about 32 nm.The high-pressure application transforms the & beta;polymorph of theLiGaO(2) into a trigonal & alpha; structure at the pressureof about 3 GPa. Further increase of pressure quenches Fe3+ luminescence due to the amorphization process of the material. A 0.25% iron (Fe3+)-doped LiGaO2 phosphorwas synthesized by a high-temperature solid-state reaction method.The phosphor was characterized utilizing X-ray diffraction (XRD),scanning electron microscopy (SEM), high-pressure photoluminescence,and photoluminescence decay measurement techniques using diamond anvilcells (DACs). The powder X-ray analysis shows that the phosphor isa & beta; polymorph of LiGaO2 with an orthorhombic crystallographicstructure at room temperature. The SEM result also confirms the presenceof well-dispersed micro-rod-like structures throughout the sample.The photoluminescence studies in the near-infrared (NIR) range wereperformed at ambient, low-temperature, and high-pressure conditions.The synthesized phosphor exhibits a photoluminescence band around746 nm related to the T-4(1) & RARR; (6)A(1) transition with a 28% quantum efficiency at ambientconditions, which shifts toward longer wavelengths with the increaseof pressure. The excitation spectra of Fe3+ are very wellfitted with the Tanabe-Sugano crystal-field theory. The phosphorluminescence decays with a millisecond lifetime. The high-pressureapplication transforms the & beta; polymorph of LiGaO2 intoa trigonal & alpha; structure at the pressure of about 3 GPa. Furtherincrease of pressure quenches the Fe3+ luminescence dueto the amorphization process of the material. The prepared phosphorexhibits also mechanoluminescence properties in the NIR spectral region.