Collaborative: EAGER: Demonstration that Thin Film Phase Transformations Can Be Monitored at High-Temperature and High-Pressure in a Diamond Anvil Cell

相变和相关的体积变化强烈地影响着材料的性质。当它们出现在俯冲带中的矿物中时--一个构造板块俯冲到另一个板块之下--它们可能会引发地震。初步观察表明，相界(发生转变的地方)受到矿物颗粒大小和应力状态变化的影响。然而，由于实验的限制，人们对这种影响仍然知之甚少。事实上，在俯冲带普遍存在的极端压力和温度下调整矿物的粒度和应力状态是具有挑战性的。在这里，研究人员探索了一种新的实验方法的能力，这种方法允许这种调整。他们使用最先进的沉积技术生产颗粒大小和应力状态可控的矿物薄膜。然后，他们使用高压设备探测地球深处极端条件下的矿物稳定性。这项工作促进了材料科学和矿物物理之间的技术转移。它的结果具有广泛的影响，特别是关于用于日常设备的薄膜的稳定性。该项目还为在多学科环境中培训的研究生提供了支持。在这里，通过调节生长条件和衬底的选择，通过脉冲激光沉积制备了具有不同微晶尺寸和双向应力状态的二氧化硅(SiO_2)薄膜。然后将这些薄膜放置在钻石砧座单元的独立调制的静液压应力场中。这种高压装置可以在两颗相对的钻石尖端产生非常高的压力。在不同的压力和温度下，用可见光和/或X射线原位探测了薄膜的性质。我们的目标是找出给定的二氧化硅微晶尺寸和/或双向应力状态如何改变二氧化硅相界的压力和温度条件。更广泛地说，该团队探索脉冲激光沉积能否产生具有可调应力状态、微晶大小和取向的地质相关薄膜。这样一种新的工具可能会对研究地球深处发生的相变以及与运输性质和化学反应相关的其他过程产生革命性的影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Phase transitions and the associated volume changes strongly influence materials’ properties. When occurring in minerals in subduction zones - where one tectonic plate dives underneath another - they may cause earthquakes. Preliminary observations suggest that phase boundaries (where transitions occurred) are influenced by changes in mineral grain size and stress state. However, such effects are still poorly understood because of experimental limitations. Indeed, it is challenging to tune minerals’ grain size and stress state at the extreme pressures and temperatures prevailing in subduction zones. Here, the researchers explore the capabilities of a new experimental approach which allows such tuning. They produce thin films of mineral with controlled grain size and stress state using state-of-the-art deposition techniques. They then probe the mineral stability at the extreme conditions of the deep Earth using high-pressure devices. This work fosters technological transfers between Materials Science and Mineral Physics. Its outcomes have broad implications, notably regarding the stability of thin films for incorporation into everyday devices. The project also provides support for a graduate student trained in a multidisciplinary environment.Here, silica (SiO2) thin films with variable crystallite sizes and biaxial stress states are fabricated via Pulsed Laser Deposition by modulating the growth conditions and choice of substrate. These thin films are then placed within the independently modulated hydrostatic stress field of a diamond anvil cell. This high-pressure device can produce very high pressures at the tips of two opposing diamonds. The films’ properties are probed in situ with visible light and/or x-rays at various pressures and temperatures. The goal is to map out how given SiO2 crystallite size and/or biaxial stress state changes the pressure and temperature conditions of silica phase boundaries. More generally, the team explores whether Pulsed Laser Deposition can produce geologically relevant thin films with tunable stress states, crystallite sizes and orientations. Such a novel tool could be transformative for the study of phase transformations - as well as other processes related to transport properties and chemical reactions - occurring in the deep Earth.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.