Effect of Crystallographic Orientation on the Dielectric Properties of (Nb _0.5 Ga _0.5 ) _0.5% Ti _99.5% O ₂ Single Crystals

(Nb0.5Ga0.5)0.5%Ti99.5%O2 single crystals were successfully grown using the Verneuil method, and the anisotropy of its dielectric properties was systematically investigated. Characterization revealed that (Nb0.5Ga0.5)0.5%Ti99.5%O2 single crystals exhibit significant dielectric anisotropy, with the dielectric constant showing an inverse relationship with bandgap width. The (310) crystal orientation exhibited the narrowest bandgap, facilitating enhanced electron transitions and yielding the highest dielectric constant. Furthermore, the orientation-dependent atomic arrangement altered the dominant polarization mechanisms, accounting for the observed dielectric anisotropy. Defect clusters in the (200), (210), and (310) orientations exhibit weaker binding of free electrons, enabling the formation of off-domain electrons. These mobile charges induce slow polarization mechanisms, resulting in increased dielectric loss and degraded frequency stability. Significant electron orbital hybridization between Ti 3d, O 2p, Ga 4p and Nb 4d orbitals in the (002) and (110) crystal orientations localizes the free electrons, and the dielectric properties are dominated by the EPDD polarization, yielding much more excellent dielectric properties. This work provides a new avenue for the preparation of high-performance TiO2-based giant dielectric materials by combining defect engineering and crystal plane orientation.