新型热障涂层陶瓷La_(2-x)Gd_xWMoO_9的制备及其热物理性能研究

Synthesis and Thermo-physical Properties of Novel La_(2-x)Gd_xWMoO_9 Ceramics for Thermal Barrier Coatings

采用溶胶-凝胶自蔓延合成工艺,以Gd3+作为掺杂离子,以(NH4)6Mo7O24·4H2O,H40N10O41W12·xH2O及La(NO3)3·6H2O为前驱体原料,合成了La2-xGdxWMoO9系(LGWMO,x=0,0.1,0.2,0.3)陶瓷粉体。通过放电等离子烧结技术(SPS)制备出LGWMO系高致密陶瓷材料,借助XRD、激光热导仪、热膨胀系数测试仪、SEM等分析技术对材料的物相组成、热扩散系数、热膨胀系数、微观形貌等性能进行表征;研究了Gd3+离子掺杂量对LGWMO系材料热导率、热膨胀系数的影响。结果表明:少量Gd3+的掺杂(x<0.1)能降低La2WMoO9陶瓷材料的热导率,但不利于La2WMoO9陶瓷热膨胀系数的提高;在Gd3+掺杂量x=0.1时,La1.9Gd0.1WMoO9陶瓷材料具有最佳的热物理性能:热导率λ=0.65W·m-1·K-1(T=298K);热膨胀系数αL=15.04×10-6K-1(T=1273K)。

La2-xGdxWMoO 9 (LGWMO, x=0.0, 0.1, 0.2, 0.3) powder for thermal barrier coatings (TBCs) has been synthesized from sol-gel self-propagating process using (NH4)6Mo7O24 ·4H2O, H40N10O41W12 ·xH2O and La(NO3)3 ·6H2O as precursor and doped with Gd3+ . Highly dense La2-xGd xWMoO9 bulk ceramics were prepared by spark plasma sintering (SPS). The phases of sintered bulk materials, thermal diffusivity, thermal expansion coefficient and microstructure were characterized by X-ray diffraction, laser-flash thermal conductivity tester, high-temperature dilatometer and scanning electron microscopy (SEM), respectively. The thermo-physical properties of the LGWMO ceramics were compared as a function of doped content of Gd3+ . Results suggest that Gd 3+ doping in small quantity (x<0.1) is beneficial to decrease the thermal conductivities of LGWMO materials, but not to increase thermal expansion coefficient. The optimal thermo-physical properties of La2-xGdxWMoO9 is achieved (λ=0.65 W·m-1 ·K-1 at T=298 K;α L =15.04×10-6 K-1 at T=1273 K) when the doping content of Gd3+ is at 0.1.