Thermophysical properties of the ternary oxides NbAlO4 and TaAlO4 are experimentally determined. For NbAlO4, the molar heat capacity is 98.9 J (mol \(\cdot\) K)−1 at 0 \(^{\circ }\) C up to 155.6 J (mol \(\cdot\) K)−1 at 950 \(^{\circ }\) C and for TaAlO4 97.1 J (mol \(\cdot\) K)−1 at 0 \(^{\circ }\) C up to 154.2 J (mol \(\cdot\) K)−1 at 950 \(^{\circ }\) C, respectively. Maier-Kelley polynomials are provided for the molar heat capacities. Thermal diffusivities in the range from 20 \(^{\circ }\) C to 700 \(^{\circ }\) C ( \(\alpha _{NbAlO_{4}}\) : from 0.009 to 0.004 cm2·s−1 and \(\alpha _{TaAlO_{4}}\) : from 0.017 to 0.005 cm2·s−1), bulk densities at 25 \(^{\circ }\) C ( \(\rho _{NbAlO_{4}}\) = 3.94 g \(\cdot\) cm−3 and \(\rho _{TaAlO_{4}}\) = 6.07 g·cm−3) and melting points of the oxides are measured, and the thermal conductivities are calculated from these properties. The thermal conductivity from 20 \(^{\circ }\) C to 700 \(^{\circ }\) C of NbAlO4 \(\lambda _{ NbAlO_{4}}\) is in the range from 0.020 to 0.013 W·cm−1·K−1 and of TaAlO4 \(\lambda _{TaAlO_{4}}\) in the range from 0.039 to 0.015 W·cm−1·K−1, respectively. A porosity correction for thermal conductivities is applied, and with that, data for perfectly dense material are provided.
