Synthesis and Thermophysical Properties of La_2Zr_2O_7/SrZrO_3 Composite as a New Thermal Barrier Coating Material

摘要

The La_2Zr_2O_7/SrZrO_3 composite with a mol ratio of 1:2 named (La_(0.5)Sr_(0.5))ZrO_(3.25) (LSZ) was in-situ synthesized by co-precipitation method using ammonia and ammonium oxalate as precipitants. The synthesized LSZ powder showed good phase stability not only from room temperature to 1400°C but also at higher temperature of 1450°C for a long period, as analyzed by thermogravimetry, differential scanning calorimetry and x-ray diffraction, respectively. The bulk LSZ with relative density >95% was prepared by pressureless sintering at 1500°C for 2 h and spark plasma sintering (SPS) at 1300°C for 5 min, respectively. The fracture toughness of the bulk LSZ prepared by both pressureless sintering and SPS were 1.80±0.20 MPa-m~(1/2) and 1.95±0.09 MPa-m~(1/2), respectively, which are higher than that of both bulk SrZrO_3 and La_2Zr_2O_7. The coefficients of thermal expansion (CTEs) of the bulk LSZ were 8.4-9.5×10~(-6)K~(-1) in a temperature range of 200-1200°C , which are higher than that of La_2Zr_2O_7 but lower than that of SrZrO_3. The thermal conductivity of the bulk LSZ prepared by pressureless sintering was ~1.1 W-m~(-1) ?K~(-1) at 1000°C , which is lower than that of both bulk SrZrO_3 and La_2Zr_2O_7. The LSZ composite is considered as a promising thermal barrier coating material.