Spectroscopic Studies of High Permittivity Materials

高介电常数材料由于在移动电话网络中的重要应用以及在静电储能设备(电容器)中的潜在应用而引起人们的极大兴趣。要想在电容器中得到潜在的应用，材料需要与温度无关的“巨介电常数”。介质谐振器是移动电话网络中的常见部件，要想在其中发挥潜在的作用，必须在保持合理的高介电常数和与温度无关的介电常数的同时，将能量“损耗”降至最低。这项研究提案将解决与这两个应用有关的基本问题。自2013年以来，人们一直认为在两种新型材料中观察到了巨介电常数：一种是由于缺陷偶极子引起的介电常数增加，另一种是介电常数增加不被理解的高熵氧化物。最近的测试表明，共掺杂氧化物中巨介电常数的观测受到电接触的强烈影响。关于“缺陷偶极子”是否真的可以增加介电常数这一悬而未决的问题，将使用补偿硅中的一种无接触技术进行研究。如果这一机制被证明是可能的，它可能导致共掺杂高禁带材料的发展，这可能是有用的能量存储。我们还将在高熵氧化物中进行测试，看看之前通过测量低频电容所观察到的巨介电常数是否同样受到电接触的影响。关于介质谐振器材料，请注意，常用的损耗最低的材料，有序的钙钛矿型BaMg1/3Ta2/303，因为它包含了Ta，所以非常昂贵。许多研究人员建议使用基于Nb的材料来取代昂贵的Ta。然而，目前人们对铌基材料的损耗机理知之甚少。例如，虽然BaMg1/3Nb2/3O3的损耗被预测为足以用于谐振器应用，但到目前为止，在生产的样品中观察到的损耗非常大。本提案所要求的资金将用于利用X射线衍射和宽频率范围介电光谱学相结合的方法，对基于Nb的介质谐振器材料中的介电损耗进行系统研究。目的是了解是否可以稍微修改化学成分和工艺条件以减少损失。开发一种能够在性能和价格上与钽基材料竞争的铌基材料将是一项重大而有用的成就。

High Permittivity materials are of great interest because of important existing applications in cell phone networks and potential applications in electrostatic energy storage devices (capacitors). To be of potential use in capacitors, a material will require "giant permittivity" that is temperature independent. To be of potential use in a dielectric resonator, which is a common component in cell phone networks, the energy "loss" must be minimized, while maintaining a reasonably high and temperature-independent permittivity. This research proposal will address fundamental questions regarding both of these applications. Since 2013, giant permittivity has been thought to have been observed in two novel materials: "co-doped oxides" in which the permittivity increase is due to “defect dipoles” and "high entropy oxides" in which the permittivity increase is not understood. Recent tests have suggested that the observation of giant permittivity in co-doped oxides is strongly affected by electrical contacts. The open question as to whether “defect dipoles” can actually increase permittivity will be studied using a contact-free technique in compensated silicon. If this mechanism is demonstrated, it may lead to the development of co-doped higher band gap materials which may be useful in energy storage. We will also perform tests in the high entropy oxides, to see if previous observations of giant permittivity made by measuring capacitance at low frequency are similarly affected by electrical contacts. Turning to dielectric resonator materials, note that the lowest loss material commonly used, the ordered perovskite BaMg1/3Ta2/3O3, is extremely expensive because it incorporates tantalum. Many researchers have proposed using niobium-based materials to replace expensive tantalum. However, the loss mechanisms in the niobium-based materials are poorly understood. For example, while the loss in BaMg1/3Nb2/3O3 has been predicted to be good enough for resonator applications, the losses observed in samples produced up to this point in time have been very large. Funds requested in this proposal will be used to perform a systematic study of dielectric loss in niobium-based dielectric resonator materials using a combination of x-ray diffraction and wide-frequency-range dielectric spectroscopy. The goal is to understand whether chemical composition and processing conditions can be slightly modified to decrease loss. Developing a niobium based material that could compete with tantalum based materials in terms of performance and price would be a significant and useful achievement.