Mechanochemical Synthesis of Pristine and Li‐Doped Zinc Orthostannate from Separate and Blended Binary Oxide Precursors

Mechanochemistry can be considered as the top-down and bottom-up synthetic methodology, but for the latter, there are some limitations, especially regarding particle size (nanometric species). It is presented that in specific precursors’ preparation and mild mechanosynthetic conditions, these limitations may be overstepped, which results in the formation of cubic zinc orthostannate monocrystals (0.1 – 1.3 μm) embedded into the polycrystalline bodies.

Zinc orthostannate (ZTO) is a promising wide-bandgap (3.6 eV) n-type semiconductor material for various applications, and to develop efficient, facile, and relatively mild synthetic methods, we selected important advantages driving the high-temperature solid-state process and implemented them into mechanochemical reactions, and utilized the low-melting properties of metal acetates and the wetting abilities of Li-based dopants. Therefore, we report on two synthetic methods of undoped and Li-doped ZTO materials, prepared by the direct mechanochemical reactions from ZnO and SnO₂, and ZnO-SnO₂ blend, prepared at 480 °C from mechanochemically activated (500 rpm, 20 min) zinc(II) and tin(IV) acetates, are reported. The reactions’ progress is followed by ex situ powder X-ray diffractometry, Raman spectroscopy, and ultraviolet and visible light spectrometry after grinding within 20–200 min in an agate planetary ball mill at 500 rpm. The scanning electron microscopic morphological analysis uncovered the presence of monocrystalline ZTO cubes embedded in polycrystalline ZTO bodies obtained from ball milling of the Li₂O–ZnO–SnO₂ blend. These morphological changes significantly affect the bandgap from the commonly accepted 3.6 eV to about 4.0 eV. Moreover, the X-ray photoelectron spectroscopy studies showed the presence of a Zn-rich surface (Zn:Sn ratio: 5.85:1) on the starting material after thermal blending and decarbonization of precursors.

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