材料之间有一个已知的破坏规则，一组国际科学家团队的新发现增加了更多证据，以支持金属的非统治主义声誉。根据能源部劳伦斯伯克利国家实验室（伯克利实验室）和加利福尼亚大学伯克利分校的科学家领导的一项新研究，二氧化钒的电子可以在不进行热量的情况下进行电力。
这些发现于1月27日发表the journalScience，可能导致广泛的应用，例如，将发动机和电器的废热转换为电力的热电系统。
对于大多数金属，电导率与热导率之间的关系受Wiedemann-Franz定律的控制。简而言之，法律规定，良好的电力导体也是良好的热导体。金属钒二氧化钒不是这种情况，这种材料已经以其不寻常的能力从绝缘体转换为金属时，当它达到67°C或152°F时。
伯克利实验室材料科学系的物理学家，伯克利分校的材料科学与工程学教授，研究首席研究员Junqiao Wu说：“这是一个完全出乎意料的发现。”“它显示了一项教科书法的严重崩溃，该法律对传统指挥众所周知。这一发现对于理解新导体的基本电子行为至关重要。”
在学习的过程中二氧化钒的properties, Wu and his research team partnered with Olivier Delaire at DOE’s Oak Ridge National Laboratory and an associate professor at Duke University. Using results from simulations and X-ray scattering experiments, the researchers were able to tease out the proportion of thermal conductivity attributable to the vibration of the material’s crystal lattice, called phonons, and to the movement of electrons.
To their surprise, they found that the thermal conductivity attributed to the electrons is ten times smaller than what would be expected from the Wiedemann-Franz Law.
“The electrons were moving in unison with each other, much like a fluid, instead of as individual particles like in normal metals,” says Wu. “For electrons, heat is a random motion. Normal metals transport heat efficiently because there are so many different possible microscopic configurations that the individual electrons can jump between. In contrast, the coordinated, marching-band-like motion of electrons in vanadium dioxide is detrimental to heat transfer as there are fewer configurations available for the electrons to hop randomly between.”
值得注意的是，二氧化钒可以进行的电力和热量通过将其与其他材料混合来调整。当研究人员用金属钨掺杂单晶钒样品时，他们降低了二氧化钒变成金属的相变温度。同时，金属相中的电子成为更好的热导体。这使研究人员能够控制二氧化钒可以通过在可调温度下切换到金属的热量来消散的热量。
研究人员说，这些材料可用于帮助清除或消散发动机中的热量，或者被开发成窗涂层，以改善建筑物中能源的有效利用。
研究共同领导作者Yang说：“这种材料可用于帮助稳定温度。“通过调整其导热率，该材料可以在炎热的夏季有效并自动散发热量，因为它的导热率很高，但由于其在较低温度下的导热率低，因此可以防止在寒冷的冬季进行热量损失。”
二氧化钒具有额外的好处，即在约30°C（86°F）以下透明，并吸收60°C（140°F）的红外光。
杨指出，在二氧化钒可以商业化之前，还有更多的问题需要回答，但说这项研究突出了具有“异国情调的电气和热性能”材料的潜力。
While there are a handful of other materials besides vanadium dioxide that can conduct electricity better than heat, those occur at temperatures hundreds of degrees below zero, making it challenging to develop into real-world applications, the scientists said.
Other co-lead authors of the study include Sangwook Lee at Kyungpook National University in South Korea, Kedar Hippalgaonkar at the Institute of Materials Research and Engineering in Singapore, and Jiawang Hong at the Beijing Institute of Technology in China. Lee and Hippalgaonkar started work on this paper as postdoctoral researchers at UC Berkeley. Hong began his work as a postdoctoral researcher at Oak Ridge National Laboratory. The full list of authors可在线提供。
通过使用DOE科学办公室的电子材料计划支持的设施，对这项工作的额外支持。
