Study on the Solid and Solution Properties of Sc3+ and Al3+ in (Tb, Sc)3 (Sc, Al)5O12 Crystals Grown by the Czochralski Method

Terbium scandium aluminum garnet crystals (Tb3Sc2Al3O12, TSAG) have excellent optical comprehensive properties with unique competitive advantages in the Verdet constant and anti-laser damage threshold. However, the component segregation will easily occur during the growth of the TSAG crystal and the distribution habits of elements in crystals have not been systematically studied. A series of TSAG crystals with different compositions were grown by the Czochralski method in this work. The behaviors of Sc3+ and Al3+ in TSAG crystal growth were discussed, and the relationship between TSAG crystal cracking and crystal structure was deeply studied. The results show that the segregation coefficient of Al in the TSAG melt solid system is 1.02–1.03, while that of Sc is 0.94–0.97. It is observed by spherical aberration-corrected transmission electron microscopy that Sc3+ entered into the dodecahedron in the space where Tb3+ was located during the crystal growth, which explains that the composition ratio of Tb:(Al + Sc) in TSAG crystals was less than the stoichiometric ratio of 3:5. Crystals with a lower Sc content are not easy to crack during the growth and have high light transmittance (>80%), excellent thermal stability, and stronger magneto-optical properties.