Thermal conduction behavior in polycrystalline (Sr _1-x ,K _2x )Zr ₄ (PO ₄ ) ₆ ceramic

Single-phase (Sr _1-x ,K _2x )Zr ₄ (PO ₄ ) ₆ ceramic (with x=0.0-0.8) demonstrated values of thermal conductivity decrease with increasing potassium content to a minimum value at x=0.5, which suggests a maximum content of lattice defect, i.e., oxygen vacancy, at this composition. The thermal conductivity of the ceramic then increased with further increase of potassium. The thermal conduction in (Sr _1-x ,K _2x )Zr ₄ (PO ₄ ) ₆ ceramic (at x=0.5) appears to exhibit a strongly lattice-defect dependence with a calculated phonon mean free path of approximately 3.04 Å, rather than a phonon-phonon dependence as observed in a number of dielectric materials. A linear relationship of the thermal conductivity in terms of porosity with temperature up to 600°C has been correlated and can be simply expressed as K=K ₀ (1-p) regardless of the influence of emissivity factor.