Suppressing the phase transition of ZrP₂O₇ by defect and entropy regulation for high-temperature wave-transparent material application

ZrP₂O₇ is a promising wave-transparent material due to its low dielectric constant and low dielectric loss, but its inherent phase transition characteristic at approximately 300 °C limits its high-temperature application. Therefore, suppressing the phase transition is necessary for ZrP₂O₇ to serve in extremely harsh environments. In this work, introducing Ti and Hf into ZrP₂O₇ causes significant lattice distortion and an increase in entropy, both of which synergistically limit the crystal structure transformation. In addition, enhanced phonon scattering by mismatch of atomic mass and local distortion leads to a reduction in the thermal conductivity. Lattice distortions also cause changes in both bond length and tilting angle, so that (Ti_1/3Zr_1/3Hf_1/3)P₂O₇ does not undergo sudden expansion as does ZrP₂O₇. (Ti_1/3Zr_1/3Hf_1/3)P₂O₇ maintains excellent dielectric properties, which highlights it as a promising high-temperature wave-transparent material.