Toward High-Throughput Thermal Characterization of Combinatorial Thin-Film Solid State Phase Change Materials

Phase change materials (PCMs) offer a passive methodology to store thermal energy and mitigate transient temperature increases. Those that go from one solid-state phase to another remove the need for confinement structures imposed by PCMs which melt or sublimate. The use of solid-to-solid state phase change materials is an emerging topic of interest, and the parameters governing the use of such materials in high power applications (namely, thermal conductivity, latent heat, volumetric specific heat, and transformation temperature) are not well-understood in solid-to-solid metallic PCMs (such as those exhibiting reversible Martensitic transformations). It has been demonstrated that thermal conductivity, latent heat, and transformation temperature in these systems can be significantly tailored by adjusting the processing conditions, but little data exists on the impact of compositional variants of ternary or quaternary elements exhibiting the shape memory effect. A main limitation is the lack of rapid, high-throughput experimental methodologies capable of characterizing these quantities to better inform design of materials. In this work, we demonstrate efficacy of a finite element method to explore parametric spaces for designs of test structures capable of simultaneously resolving thermal conductivity, specific heat, latent heat, and transformation temperature. Test structures will be fabricated using photolithography and thin film deposition techniques capable of combinatorial thin film fabrication. The goal of this work is to determine whether the proposed design - a thermally isolated suspended platform - will be capable of resolving transient and frequency-domain thermal signal to recover the desired properties. This work relies on finite element modeling using multiphysics software COMSOL v5.5 to predict experimental sensitivity to the input parameters, and will ultimately rely on coupling finite element models to fitting algorithms to determine unknown material properties. This combined thermal characterization strategy represents a leap-ahead for PCM characterization capabilities. Rapid characterization of wide compositional variations will enable accelerated progress in leveraging PCMs for high power applications.