Comprehensive Structural and Optical Characterization of Zinc-Doped Gadolinium Titanate Pyrochlore Solid Solutions

A novel pyrochlore solid solution GTZ, was synthesized via a solid-state reaction in order to establish a clear structure–property relationship. X-ray diffraction and Rietveld refinement confirmed the formation of a single-phase cubic pyrochlore up to an ZnO solubility limit of x ≈ 0.35. Refinement showed that Zn2+ substituted for Gd3+ on the A-site, resulting in systematic lattice contraction and the creation of charge-compensating oxygen vacancies. This targeted structural modification enhances both optical and ionic properties simultaneously. Optically, the band gap was tuned from 3.63 eV to 3.74eV. More significantly, this resulted in a substantial enhancement of the nonlinear optical response, with the nonlinear refractive index (n₂) increasing by over two orders of magnitude to an impressive 3.10×10-10esu. Concurrently, bond valence energy landscape (BVEL) calculations predicted a dramatic decrease in the activation energy for oxygen ion migration, from 1.115eV to 0.514eV. This work demonstrates that A-site doping is a powerful strategy for creating multifunctional materials with exceptionally strong nonlinear optical properties and high ionic mobility, highlighting their significant potential for advanced photonic and electrochemical applications.