The thermal transport properties—thermal diffusivity, thermal conductivity and specific heat
capacity—of potassium selenate crystal have been measured through the successive phase
transitions, following the photo-pyroelectric thermal wave technique. The variation of thermal
conductivity with temperature through the incommensurate (IC) phase of this crystal is
measured. The enhancement in thermal conductivity in the IC phase is explained in terms of
heat conduction by phase modes, and the maxima in thermal conductivity during transitions is
due to enhancement in the phonon mean free path and the corresponding reduction in phonon
scattering. The anisotropy in thermal conductivity and its variation with temperature are
reported. The variation of the specific heat with temperature through the high temperature
structural transition at 745 K is measured, following the differential scanning calorimetric
method. By combining the results of photo-pyroelectric thermal wave methods and differential
scanning calorimetry, the variation of the specific heat capacity with temperature through all the
four phases of K2SeO4 is reported. The results are discussed in terms of phonon mode softening
during transitions and phonon scattering by phase modes in the IC phase.