Recent development of A2B2O7 system transparent ceramics

A(2)B(2)O(7) system compounds, which usually present three phase structures mainly based on the ionic radius ratios of r(A) and r(B) (r(A)/r(B)), have been studied for potential applications in many fields, such as thermal barrier coatings, luminescence powders, fast-ion conductors, photocatalysts, and matrices for immobilization of highly active radionuclides. Since 2005, La2Hf2O7 was fabricated into transparent ceramics and much more attentions were paid on A(2)B(2)O(7) transparent ceramics for new applications. In this review, the development of A(2)B(2)O(7) system transparent ceramics was described. The structure characteristics, powder synthesis method, and sintering techniques of the final A(2)B(2)O(7) transparent ceramics were summarized. After that, the mostly reported A(2)Hf(2)O(7), A(2)Zr(2)O(7), and A(2)Ti(2)O(7) system transparent ceramics were systematically introduced. The potential application fields and future development trends were also discussed, focusing on scintillators, optical elements, and other luminescent materials