Scientists at the Technical University of Denmark have created a novel microscope that substantially improves the measurement of heat flow in materials, according to a study published in Science Advances. This development could result in better designs for energy systems and technological devices.
High-resolution thermal diffusivity area maps of Bi2Te3. Illustration of the results using the M4PP setup to map the thermal diffusivity of the Bi2Te3 grains of different orientations. (A) The measured thermal diffusivity using the M4PP in X-scan direction and (B) the measured thermal diffusivity using the M4PP in Y-scan direction. The thermal diffusivity values obtained in the two different scan directions are encoded in the color code to the right. The upper limit of the color bar corresponds to the cutoff at 1.8 mm2/s. (C) EBSD images of the grains, in IPF map notation and an eye guide arrow indicating the normal [001] of the crystal structure. (D) is an optical image of the Bi2Te3 grains. Image Credit: © 2025 The Authors. DOI: 10.1126/sciadv.ads653.
Measuring heat movement through materials is critical for creating efficient electronics and energy devices. Improved heat management can result in faster and more dependable computers, as well as more efficient solar panels and batteries.
Finding the right materials for electronics is crucial in developing the devices we need to support the green transition. For instance, when turning heat into electricity – or vice versa - we need materials that lose very little heat but at the same time are great electrical conductors.
Nini Pryds, Professor, Technical University of Denmark
“To that end, we want to find out how heat is dispersed in the materials we use. By observing this, we can determine how heat moves in different directions within the material, which is important because it affects their performance,” Pryds added.
The trick is to identify materials that operate consistently on the nanometer scale. At this scale, minor variations in heat conductivity can significantly impact the material's overall performance. For example, heat can be transferred in different ways depending on the arrangement of crystals, grain size, or shape, affecting the material's ability to convert heat into electricity—its thermoelectric capabilities—and thus leading to a less effective device.
There are methods for studying heat transport, but they are frequently slow, involve sophisticated setups, or risk harming the materials under investigation. This has made it difficult for researchers to obtain accurate and reliable data to assess their performance.
It Takes a Microscope
The scientists devised a new microscopy technology to overcome these issues in the study: a thermal diffusivity microscope. The entirely automated CAPRES microRSP measurement platform serves as the foundation for the novel technique. Unlike prior approaches, no extra sample preparation is required.
The new microscope allows for high-resolution observations on a very small scale. The scientists tested two materials recognized for their superior heat and electricity conduction properties: Bi2Te3 (bismuth telluride) and Sb2Te3 (antimony telluride), which are commonly employed in thermoelectric devices that convert heat into energy.
The microscope precisely determined the directional heat flow in these materials. In other words, it can detect how heat travels in different directions, offering useful information for constructing more efficient systems. The findings were confirmed by comparing the novel method to existing established techniques, demonstrating the microscope's reliability and effectiveness.
“I believe our new microscopy method is a significant step forward in the field of materials science. We have developed a fast, simple, and non-damaging way to measure heat flow that gives us a better understanding of how these materials behave,” Pryds concluded.
Journal Reference:
Lamba, N. et al. (2025) Thermal diffusivity microscope: Zooming in on anisotropic heat transport. Science Advances. doi.org/10.1126/sciadv.ads6538