Defect engineering via doping exhibits considerable potential for improving the performance of environment-friendly lead-free piezoelectric materials. Owing to the susceptibility to lattice vibrations and the micro-local chemical environment, the readily available Mn/Fe transition metal elements (TMEs) facilitate the construction of defect structures. However, the role of TMEs in shaping the domain structures and the corresponding promotional mechanism of piezoelectricity need to be further decoded. Herein, we propose the different influence mechanisms of Mn and Fe ions on the ferroelectric domain and piezoelectric properties. Different concentrations of (MnNb/Ta′-VO••)• and (FeNb/Ta″-VO••)× defect dipoles are obtained based on the synergy of Mn/Fe ions with oxygen vacancies. Diverse ferroelectric behaviors resulting from (MnNb/Ta′-VO••)• and (FeNb/Ta″-VO••)× defect dipoles are observed. Furthermore, the variation of the dielectric diffusiveness with the defect dipole concentration is investigated. Trace concentration of (MnNb/Ta′-VO••)• generates strong diffusiveness. With the characterization of the ferroelectric domain, this strong diffusiveness is attributed to the lattice-like domain structure. Thereafter, the mechanisms of Mn/Fe defect dipoles on the formation of domain structures are clarified. Macroscopically, the dielectric and piezoelectric properties are measured with Mn/Fe ion components. Trace Mn doping and the resulting lattice-like domain significantly enhance the piezoelectric coefficient, resulting in an increase of nearly 50% for K(Ta,Nb)O3 single crystals. This work highlights the tremendous potential of TME-induced defect dipoles for modifying the ferroelectric domain and provides a reference paradigm for improving piezoelectricity through defect engineering.

中文翻译：

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Mn/Fe掺杂KTN晶体中缺陷浓度对压电性的影响

通过掺杂进行缺陷工程在提高环保无铅压电材料的性能方面表现出巨大的潜力。由于对晶格振动和微局部化学环境的敏感性，容易获得的Mn/Fe过渡金属元素（TME）有利于缺陷结构的构建。然而，TME 在塑造域结构中的作用以及相应的压电促进机制需要进一步解码。在此，我们提出了Mn和Fe离子对铁电畴和压电性能的不同影响机制。基于Mn/Fe离子与氧空位的协同作用，获得了不同浓度的(MnNb/Ta'-VO••)•和(FeNb/Ta"-VO••)×缺陷偶极子。观察到由(MnNb/Ta′-VO••)• 和(FeNb/Ta"-VO••)× 缺陷偶极子产生的不同铁电行为。此外，还研究了介电扩散率随缺陷偶极子浓度的变化。微量浓度的(MnNb/Ta′-VO••)•会产生很强的扩散性。根据铁电畴的表征，这种强扩散性归因于晶格状畴结构。此后，阐明了Mn/Fe缺陷偶极子对域结构形成的机制。宏观上，介电和压电特性是用Mn/Fe离子成分测量的。微量Mn掺杂和由此产生的晶格域显着提高了压电系数，导致K(Ta,Nb)O3单晶的压电系数增加了近50%。这项工作凸显了 TME 诱导的缺陷偶极子在改变铁电畴方面的巨大潜力，并为通过缺陷工程改善压电性提供了参考范例。