High-Pressure Synthesis and Local Structure of Corundum-Type In2-2xZnxSnxO3 (x ≤ 0.7)

The corundum-type In2-2xZnxSnxO3 solid solution (cor-ZITO, x <= 0.7) was synthesized at 1000 degrees C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In2-2xZnxSnxO3 (x <= 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO3. Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO3-type arrangemert.