Preparation and characterization of SrZrO3-La2Ce2O7 composite ceramics as a thermal barrier coating material

The (1-x)SrZrO3-xLa(2)Ce(2)O(7)(x = 0, SZ; x = 0.3, S7L3; x = 0.5, S5L5; x = 0.7, S3L7; x = 1, LC) composite powders were synthesized by a coprecipitation-calcination method. The composite bulks were fabricated by pressureless sintering at 1600 degrees C for 6 h. The X-ray diffraction (XRD) results indicated that the SZ-LC composite powders and bulks were comprised of the SZ and/or LC phase. The S7L3 and S5L5 bulks showed higher microhardness both in the as-sintered state and after heat-treatment at 1450 degrees C for different times. Their thermal expansion coefficients (TECs) revealed a positive effect on the phase transitions of the SZ-LC bulks. The composite bulks showed good phase stability from room-temperature to 1400 degrees C, determined by thermal analysis apparatus (DSC) and TEC analyses. The S5L5 bulk had very low thermal conductivity (0.97 W m(-1) K-1, 1200 degrees C) compared with SZ and 8 wt% Y2O3-stabilized ZrO2 (8YSZ) over the same temperature range. Therefore, the S5L5 composite ceramics is considered to be a potential material for thermal barrier coating applications at higher temperatures than 8YSZ.