Structural, Electrical, and Optical Properties of the Tetragonal, Fluorite-Related Zn_0.456In_1.084Ge_0.460O₃

We report the discovery of Zn_0.456In_1.084Ge_0.460O₃, a material closely related to bixbyite. In contrast, however, the oxygen atoms in this new phase occupy 4 Wyckoff positions, which result in 4 four-coordinate, 24 six-coordinate (2 different Wyckoff positions), and 4 eight-coordinate sites as compared to the 32 six-coordinate (also 2 different Wyckoff positions) sites of bixbyite. This highly ordered material is related to fluorite, Ag₆GeSO₈, and -UO₃ and is n-type with a bulk carrier concentration of 4.772 × 10¹⁴ cm^-3. The reduced form displays an average room temperature conductivity of 99(11) S·cm^-1 and an average optical band gap of 2.88(1) eV. These properties are comparable to those of In₂O₃, which is the host material for the current leading transparent conducting oxides. The structure of Zn_0.456In_1.084Ge_0.460O₃ is solved from a combined refinement of synchrotron X-ray powder diffraction and time-of-flight neutron powder diffraction and confirmed with electron diffraction. The solution is a new, layered, tetragonal structure in the I4₁/amd space group with a = 7.033986(19) Å and c = 19.74961(8) Å. The complex cationic topological network adopted by Zn_0.456In_1.084Ge_0.460O₃ offers the potential for future studies to further understand carrier generation in -3 eV oxide semiconductors.