Structural, Electrical, and Optical Properties of
the Tetragonal, Fluorite-Related Zn<sub>0.456</sub>In<sub>1.084</sub>Ge<sub>0.460</sub>O<sub>3</sub>
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Abstract
We report the discovery of Zn<sub>0.456</sub>In<sub>1.084</sub>Ge<sub>0.460</sub>O<sub>3</sub>, 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, Ag<sub>6</sub>GeSO<sub>8</sub>, and γ-UO<sub>3</sub> and is n-type with a bulk carrier concentration of 4.772 ×
10<sup>14</sup> cm<sup>–3</sup>. The reduced form displays
an average room temperature conductivity of 99(11) S·cm<sup>–1</sup> and an average optical band gap of 2.88(1) eV. These properties
are comparable to those of In<sub>2</sub>O<sub>3</sub>, which is the
host material for the current leading transparent conducting oxides.
The structure of Zn<sub>0.456</sub>In<sub>1.084</sub>Ge<sub>0.460</sub>O<sub>3</sub> 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 <i>I</i>4<sub>1</sub>/<i>amd</i> space group with <i>a</i> =
7.033986(19) Å and <i>c</i> = 19.74961(8) Å. The
complex cationic topological network adopted by Zn<sub>0.456</sub>In<sub>1.084</sub>Ge<sub>0.460</sub>O<sub>3</sub> offers the
potential for future studies to further understand carrier generation
in ∼3 eV oxide semiconductors
