Comprehensive Measurement of Three-Dimensional Thermal Conductivity Tensor Using a Beam-Offset Square-Pulsed Source (BO-SPS) Approach

TL;DR

This paper introduces the BO-SPS method for precise, comprehensive measurement of three-dimensional thermal conductivity tensors in anisotropic materials, overcoming limitations of existing techniques.

Contribution

The study presents a novel BO-SPS approach that accurately isolates tensor elements using square-pulsed heating and temperature measurements, validated on quartz samples.

Findings

Successfully measured full thermal conductivity tensors for quartz samples.

Achieved high signal-to-noise ratios even with large beam offsets.

Validated the method's reliability and accuracy in complex materials.

Abstract

Accurately measuring the three-dimensional thermal conductivity tensor is essential for understanding and engineering the thermal behavior of anisotropic materials. Existing methods often struggle to isolate individual tensor elements, leading to large measurement uncertainties and time-consuming iterative fitting procedures. In this study, we introduce the Beam-Offset Square-Pulsed Source (BO-SPS) method for comprehensive measurements of three-dimensional anisotropic thermal conductivity tensors. This method uses square-pulsed heating and precise temperature rise measurements to achieve high signal-to-noise ratios, even with large beam offsets and low modulation frequencies, enabling the isolation of thermal conductivity tensor elements. We demonstrate and validate the BO-SPS method by measuring X-cut and AT-cut quartz samples. For X-cut quartz, with a known relationship between in-plane and cross-plane thermal conductivities, we can determine the full thermal conductivity tensor and heat capacity simultaneously. For AT-cut quartz, assuming a known heat capacity, we can determine the entire anisotropic thermal conductivity tensor, even with finite off-diagonal terms. Our results yield consistent principal thermal conductivity values for both quartz types, demonstrating the method's reliability and accuracy. This research highlights the BO-SPS method's potential to advance the understanding of thermal behavior in complex materials.