TbScO3 (Terbium Scandium Oxide) or TSP (Terrbium Scandium Phosphate) is a type of optical crystal substrate material that is commonly used in various optical applications. It is known for its high refractive index, good thermal stability, and broad transparency range, making it suitable for use in a wide range of optical applications such as second harmonic generation, optical parametric oscillation, and infrared transmission. Additionally, TbScO3 has a low thermal expansion coefficient and excellent chemical stability, making it ideal for use in harsh environmental conditions.