Abstract
Yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) is one of the most important optical materials with many existing and potential future applications in laser, illumination, and scintillation. X-rays, g-rays, and UV light can induce ionization and significant changes in the valency of impurities and defects in YAG single crystals which may lead to the formation of color centers. In fact, the use of YAG crystals in laser and scintillation devices involves significant formation of color centers and requires full understanding for their characteristics and effects on the material properties. In this work, the formation and characteristics of color centers in undoped and rare-earth doped YAG single crystals was investigated mainly through optical absorption spectroscopy. An increase in the absorption over a broad range of wavelengths was observed in the as-grown sample after UV irradiation. F-centers and iron impurities in the as-grown undoped crystals were found to be responsible for the formation of color centers. However, air- or oxygen-anneal seems to be effective in suppressing most color centers in the crystals.
Highlights
Color center activation refers to the process in which a defect—such as an oxygen vacancy— traps an electron that in turn can exist in different energy levels within the trap, giving the trap special absorption and luminescence characteristics [1]
This work presents a detailed investigation of color centers in yttrium aluminum garnet (Y3Al5O12, YAG) activated by UV excitation at room temperature
The current study focuses on investigating color centers in undoped and doped YAG single crystals grown in various growth environments
Summary
Color center activation refers to the process in which a defect—such as an oxygen vacancy— traps an electron that in turn can exist in different energy levels within the trap, giving the trap special absorption and luminescence characteristics [1]. For example, optically active oxygen vacancies (VO) containing one, two, or three trapped electrons, denoted as F+-, F-, and F--centers, respectively. This work presents a detailed investigation of color centers in yttrium aluminum garnet (Y3Al5O12, YAG) activated by UV excitation at room temperature. YAG is one of the most important optical materials It is widely used in solid state lasers and has potential applications in scintillation and illumination devices. It has the garnet structure of the A3B2C3O12 form, where A, B, and C are cations, typically metals, and B and C can be the same element. The cations are organized with dodecahedral (A site), octahedral (B site), and tetrahedral (B site) coordination of oxygen ions. YAG has a lattice constant of 12 Å [2]
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