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La_2Zr_2O_7 (LZ) is a promising thermal barrier coating material for the high temperature applications. The fracture toughness and microhardness of nanocrystalline LZ (n-LZ), microcrystalline LZ (m-LZ) and LZ-5mol%8YSZ (LZ-5-8YSZ) composite (8YSZ for zirconia stabilized by 8 mol% ytrria) were studied. The n-LZ had a thermal expansion coefficient of (9.6±0.4)×10 -6 K -1 (200～1000℃) and fracture toughness of (1.98±0.07) MPa·m 1/2 which are obviously higher than those of the m-LZ ( (9.1±0.4)×10 -6 K -1 and (1.40±0.23) MPa·m 1/2, respectively), indicating that nanofication was an efficient way to increase the toughness and thermal expansion coefficient of LZ. The composite LZ-5-8YSZ had a higher fracture toughness ((1.88±0.30) MPa·m 1/2) than LZ, which was close to that of 8YSZ densified by superhigh pressure (SHP).
The fracture toughness and microhardness of nanocrystalline LZ (n-LZ), microcrystalline LZ (m-LZ) and LZ-5 mol% 8YSZ (LZ-5-8YSZ The n-LZ had a thermal expansion coefficient of (9.6 ± 0.4) × 10 -6 K -1 (200-1000 ° C) and fracture toughness of (1.98 ± 0.07) MPa · m 1/2 which are obviously higher than those of the m-LZ ((9.1 ± 0.4) × 10 -6 K -1 and (1.40 ± 0.23) MPa · m 1/2 respectively) that nanofication was an efficient way to increase the toughness and thermal expansion coefficient of LZ. The composite LZ-5-8YSZ had a higher fracture toughness ((1.88 ± 0.30) MPa · m 1/2) than LZ, which was close to that of 8YSZ densified by superhigh pressure (SHP).