Fabrication and thermal expansion properties of ZrW2O8/Zr2WP2O12 composites

ZrW2O8/Zr2WP2O12 composites were fabricated by sintering ZrW2O8–Zr2WP2O12 powder mixtures at 1473 K for 1 h, and their negative thermal expansion properties were investigated. The relative density of sintered pure-phase ZrW2O8 was 72.3%, while that of the sintered composites was 88.4–92.3%. In the composites, the observed hysteresis in the thermal expansion data was small because of the small difference between the CTEs of ZrW2O8 and Zr2WP2O12. The CTE of the composites was negative and increased with the Zr2WP2O12 content. When the Zr2WP2O12 volume fraction in the composites was increased from 0 to 75 vol%, the CTEs of the composites increased from −9.1 × 10−6 to −3.1 × 10−6 K−1 and from −5.0 × 10−6 to −1.9 × 10−6 K−1 over the temperature ranges of 323–373 and 473–673 K, respectively. In composites with Zr2WP2O12 volume fractions of 0–25 vol%, the experimentally obtained CTE values were in good agreement with the calculated values obtained by assuming mixed law behavior.