Activation and cold sintering of commercial ZnO powders: Compaction-induced oxide reduction

IF 6.2 2区材料科学 Q1 MATERIALS SCIENCE, CERAMICS

Journal of The European Ceramic Society Pub Date : 2025-08-21 DOI:10.1016/j.jeurceramsoc.2025.117769

Korbinian Aicher, Thomas Berger, Ulrich Aschauer, Oliver Diwald

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Abstract

Defect formation and changes in electronic reducibility occur during cold sintering of ZnO powder compacts. For this reason, materials design must consider the material history and processing-related changes in the electronic structure. We performed spectroscopic investigations (UV-Vis-NIR diffuse reflectance, photoluminescence, Raman, electron paramagnetic resonance) on commercially available ZnO powders that were cold-sintered in H₂O or in aqueous acetic acid as a transient phase and find significant lattice oxygen depletion in the latter case. As a result, shallow donor states emerge in UV-Vis-NIR diffuse reflectance and electron paramagnetic resonance via an isotropic resonance signal at g = 1.96. The use of NH₄Cl, instead of aqueous and/or acidic liquids as an activator to promote cold sintering, leads to identical spectroscopic fingerprints that are indicative of stoichiometry changes in ZnO. The spectroscopic results underline that cold sintering-induced protonation of the metal oxide lattice favors the formation of defects and electronic donor states.

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商用氧化锌粉末的活化和冷烧结：压实诱导的氧化物还原

氧化锌粉末在冷烧结过程中会发生缺陷形成和电子还原性的变化。因此，材料设计必须考虑材料的历史和加工过程中电子结构的变化。我们对市售的氧化锌粉末进行了光谱研究（UV-Vis-NIR漫反射、光致发光、拉曼、电子顺磁共振），这些氧化锌粉末在水或醋酸水溶液中作为瞬态冷烧结，发现后者的晶格氧消耗明显。结果，在UV-Vis-NIR漫反射和电子顺磁共振中，通过g = 1.96的各向同性共振信号出现浅供体态。使用NH4Cl，而不是水和/或酸性液体作为激活剂来促进冷烧结，导致相同的光谱指纹，这表明ZnO的化学计量变化。光谱结果表明，冷烧结诱导的金属氧化物晶格质子化有利于缺陷和电子给体态的形成。

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来源期刊

Journal of The European Ceramic Society 工程技术-材料科学：硅酸盐

CiteScore

10.70

自引率

12.30%

发文量

863

审稿时长

35 days

期刊介绍： The Journal of the European Ceramic Society publishes the results of original research and reviews relating to ceramic materials. Papers of either an experimental or theoretical character will be welcomed on a fully international basis. The emphasis is on novel generic science concerning the relationships between processing, microstructure and properties of polycrystalline ceramics consolidated at high temperature. Papers may relate to any of the conventional categories of ceramic: structural, functional, traditional or composite. The central objective is to sustain a high standard of research quality by means of appropriate reviewing procedures.