Microstructure and thermal expansion analysis of porous ZrW2O8/Al composite

•The composites are sintered at 600 °C, i.e. lower than the decomposition temperature of Al and ZrW2O8.•Low thermal expansion porous ZrW2O8/Al composites are prepared by SPS.•Surface stress on the ZrW2O8 has been dramatically reduced due to the porous structure.•Schematic structures show holes effect on the thermal mismatch stress.

Porous, phase-pure ZrW2O8/Al composites were fabricated at a temperature below the decomposition temperature of ZrW2O8 by spark-plasma-sintering (SPS). Composites were fabricated under a pressure of 65 MPa achieved 96.6% of the theoretical density, without the addition of any further sintering aids. At higher pressures, the density increased, but the γ-ZrW2O8 phase appeared due to the giant thermal mismatch between ZrW2O8 and Al, leading to an anomalously large thermal expansion on heating. Diffraction and dilatometry indicated that composites sintered at lower pressure reduced the residual stress and γ-ZrW2O8 content. These materials show low thermal expansion (4.83 × 10−6 K−1) in a temperature range of −70 to 20 °C, in good agreement with the theoretical value.