On the potential of porous ZrP2O7 ceramics for thermal insulating and wave-transmitting applications at high temperatures

Sintering at high temperature is a serious problem for porous thermal insulating ceramics. To search for sintering-resistant ceramics, ZrP2O7 is selected as the backbone material and porous ZrP2O7 ceramics with 40−60 vol% porosities and strength of 3−14 MPa are fabricated. The volume shrinkage of the 60 vol% porosity ZrP2O7 is only 1.4 % when heated at 1773 K for 6 h and the thermal conductivity, which is as low as 0.18 W m-1 K-1, keeps almost unchanged. The dielectric constants are stable in the frequency range of 7−19 GHz when the temperature increases from 298 K to 1273 K. As the porosity increases from 44 % to 60 %, the dielectric constant at 19 GHz and 1273 K decreases from 3.4 to 2.5. Good sintering-resistance, ultra-low thermal conductivity and low dielectric constant at high temperatures make porous ZrP2O7 suitable for applications as thermal insulating and wave-transmitting materials at high temperatures.