Lithium tantalate (LiTaO₃, abbreviated as LT) and lithium niobate (LiNbO₃, abbreviated as LN) are both multifunctional ferroelectric crystal materials belonging to the trigonal crystal system. They feature distorted perovskite (LT) or perovskite-like goethite (LN) crystal structures, serving as “cornerstone materials” in optoelectronics and piezoelectronics. Both materials exhibit multiple effects including piezoelectricity, ferroelectricity, electro-optics, and nonlinear optics. Lithium tantalate (LT) finds applications in infrared detection, high-frequency SAW filters, and emerging photonic chips. Lithium niobate (LN) is used in critical components such as high-speed electro-optic modulators, conventional SAW devices, and nonlinear optical devices.