Synthesis and optical properties of LaSrGaO4:RE3+ (RE = Sm, Eu, Ho) single crystals via optical float zone method

The advancement of synthesis of materials with luminescence properties of lanthanoid ions in various single crystalline host compounds with low phonon energies has facilitated the optimization of numerous materials to meet the specific optical properties required for diverse applications such as new energy resource exploration, light-emitting diodes (LEDs), quantum dot displays, laser technology, sensors, telecommunications, medical diagnostics and more. Enhanced analyses of the luminescence mechanism of lanthanoid ions in various host compounds, which have captivated researchers for many years and culminated in the development of innovative materials for optical applications. To obtain a deeper understanding of the luminescence mechanism of Sm³⁺, Eu³⁺, and Ho³⁺ ions incorporated into the Ruddlesden-Popper-type host compounds (La_1-xRE_x)SrGaO₄ (RE = Sm, Eu, Ho and x = 0; 0.05; 0.10) high quality single crystals with homogenous activator distribution grown by the optical floating zone (OFZ) method were examined systematically. X-ray diffraction (XRD) characterization shows that the compound crystallizes in a tetragonal crystal system with the space group I4/mmm (no. 139) with homogenous distribution of the dopants shown via backscattered electron (BSE) imaging. Photoluminescence studies at both 77 K and 298 K reveal that the incorporated lanthanoid ions brightly emit and even show unusual transitions due to the low cutoff phonon energy of the host compound that limits non-radiative loss pathways. Together with a high physical density of ∼6.4 g/cm³, these phosphors could be conceptualized as interesting candidates for X-ray imaging phosphors aiming at high light yields.