A double rare-earth (Yb/Y) co-doped SrZrO 3 [Sr 1.0 (Zr 0.9 Yb 0.05 Y 0.05 )O 2.95 ] thermal barrier coating was prepared via suspension plasma spraying (SPS). The rare-earth nitrates [Zr(NO 3 ) 4 ·5H 2 O, Sr(NO 3 ) 2 , Yb(NO 3 ) 3 ·6H 2 O, Y(NO 3 ) 3 ·6H 2 O] and NH 4 (C 2 O 4 ) 2 ·H 2 O were used to prepare the precursor suspension by co-precipitation. The thermal decomposition and crystallization of the precursor suspension powders calcined at 1200 °C were characterized with X-ray diffraction and a synchronous thermal analyzer coupled with quadrupole mass spectrometry . Zr 2 (C 2 O 4 ) 2 (OH) 4 decomposed into Zr(C 2 O 4 ) 2 , ZrO 2, and H 2 O initially, followed by the decomposition of Zr(CO 3 ) 2 into ZrO 2 . The SrC 2 O 4 precursor decomposed into SrCO 3 and SrO consecutively. The ZrO 2 reacted with SrO (Yb 2 O 3 , Y 2 O 3 ) to generate the Yb/Y co-doped SrZrO 3 . And the Yb/Y co-doped SrZrO 3 coating with a columnar crystal structure was prepared by SPS, which was analyzed with scanning electron microscopy, an inductively coupled plasma atomic emission spectrometer, and a laser flash analyzer. The thermal conductivity of the as-prepared coating was 1.77 W·m −1 ·K −1 at 1000 °C, which was more than 19% lower than that of the SPS SrZrO 3 coating.
Yuanming Gao,Yu Bai,Peng Zhang,Li Sun,Caiwen Liu,Hongying Dong,Qing Geng,Wei Wang,Wen Ma
In this study, the Yb–Y co-doped SrZrO 3 (SZ) coatings [SZYY-1 (Sr 1.0 (Zr 0.9 Yb 0.05 Y 0.05 )O 2.95 ), SZYY-2 (Sr 0.9 (Zr 0.9 Yb 0.05 Y 0.05 )O 2.85 ), and SZYY-3 (Sr 0.8 (Zr 0.9 Yb 0.05 Y 0.05 )O 2.75 )] were deposited by SPS (Suspension plasma spray) using the corresponding co-precipitation prepared precursors suspension. In the three as-sprayed SZYY coatings, there were some typical suspension plasma-sprayed coating structures, such as columnar crystals, vertical cracks, and micro/nanopores. The TCs (Thermal conductivities) of the three as-sprayed SZYY coatings were 1.23–1.88, 0.80–1.41, and 0.88–1.43 W/(m · K) at 100–1400 °C, respectively, which were at least 19% lower than that of the SZ coating (1.25 W/(m · K), 1000 °C). The TECs (Thermal expansion coefficients) of the three as-sprayed SZYY coatings were (7.8–8.7) × 10 −6 , (8.0–9.8) × 10 −6 , and (8.1–9.8) × 10 −6 /K, respectively (200–1360 °C). The sintering coefficients of the three as-sprayed SZYY coatings were 5.69 × 10 −6 , 4.29 × 10 −6 , and 3.84 × 10 −6 /s, respectively. The SZYY-3 coating showed the best SR (Sintering resistance), followed by the SZYY-2 coating and SZYY-1 coating. The SPS SZYY-2 coating with good phase stability, low TC (Thermal conductivity) and good SR is a promising new TBCs (Thermal barrier coatings) material. It is expected to be an alternative TBCs material for the next generation of high performance gas turbines .
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