  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.
