Used in specialized optical materials due to its luminescent properties, particularly in infrared emitters and phosphors. Employed in solid-state lasers and optical amplifiers operating in the near-infrared range. Serves as a dopant in glass and ceramic materials to enhance performance in fiber-optic communication systems. Also investigated for use in thermoelectric materials and semiconductor applications because of its unique electronic structure. Its stability at high temperatures makes it suitable for use in harsh environment sensors and coatings.