The poor fracture toughness of La₂Zr₂O₇ severely limits its application as a high temperature thermal barrier coating topcoat material. To toughen it, a ferroelastic second phase, NdAlO₃, with a Curie temperature of 1367°C has been introduced to form x NdAlO₃/(1‐x) La₂Zr₂O₇ composite ceramics by a spark plasma sintering technique, where x = 10, 20, 30, 40, and 50 mol%. The fracture toughness of sintered composite ceramic compacts is measured at both room temperature and 1200°C, respectively, by a single‐edge‐notch beam test method. The results show that, at room temperature, the residual compressive stress in the La₂Zr₂O₇ matrix plays an important role in the toughening of composite ceramics. By eliminating this factor, the remaining toughening effects agree with the measured fracture toughness at 1200°C, suggesting that the other toughening is probably ferroelastic domain switching toughening and that it is still valid at high temperature. Furthermore, the toughening effect arising from ferroelastic domain switching is governed by the overall domain switching zone, which is determined by both individual domain switching zone width and the “concentration” of ferroelastic phases. A relatively high coercive stress of NdAlO₃ and relatively low residual tensile stress in NdAlO₃ second phases contribute to negligible influence of residual tensile stress on domain switching zone width, leading to the continuous increase of fracture toughness of composite ceramics with more NdAlO₃ added at room temperature.

中文翻译：

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铁弹性NdAlO3第二相对烧绿石La2Zr2O7的增韧作用，可用于潜在的热障涂层应用

La ₂ Zr ₂ O _7的断裂韧性差，严重限制了其作为高温热障涂层面漆材料的应用。为了使其坚韧，已引入居里温度为1367°C的铁弹性第二相NdAlO ₃，以通过火花等离子体烧结技术形成x NdAlO ₃ /（1- x）La ₂ Zr ₂ O ₇复合陶瓷，其中X = 10、20、30、40和50摩尔％。烧结复合陶瓷压块的断裂韧性分别在室温和1200°C下通过单边缺口梁测试方法进行测量。结果表明，在室温下，La ₂ Zr ₂ O _7中的残余压应力基体在复合陶瓷的增韧中起着重要作用。通过消除该因素，剩余的增韧效果与在1200°C下测得的断裂韧度相符，这表明另一种增韧可能是铁弹性域转换增韧，并且在高温下仍然有效。此外，由铁弹性域转换引起的增韧效果由整个域转换区控制，该区域由单个域转换区的宽度和铁弹性相的“浓度”共同决定。NdAlO的相对高的矫顽应力₃和相对低的残余拉伸应力在NdAlO ₃第二相对残余拉伸应力对畴转换区宽度的影响可忽略不计，从而导致在室温下添加更多NdAlO ₃的复合陶瓷的断裂韧性不断提高。