Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf_1/3Zr_1/3Ce_1/3)_1-x(Y_1/2X_1/2)_xO_2-δ (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttria-stabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young’s modulus (∼210 GPa) and nanohardness (∼18 GPa). Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions.

以萤石氧化物为例，本研究将高熵陶瓷（HEC）扩大到成分复杂的陶瓷（CCC）或多原理阳离子陶瓷（MPCC），以包括中熵和/或非等摩尔成分。通式（Hf _1/3 Zr _1/3 Ce _1/3）_{1- x}（Y _1/2 X _1/2）_x O2 _-δ（X的9种成分复杂的萤石氧化物（CCFO）= Yb，Ca和Gd；x= 0.4、0.148和0.058）。测量相稳定性，机械性能和热导率。与氧化钇稳定的氧化锆相比，这些CCFO表现出增加的立方相稳定性和降低的导热性，同时保留了高的杨氏模量（〜210 GPa）和纳米硬度（〜18 GPa）。此外，非等温CCFO中随温度变化的热导率显示出类似非晶的行为。与等摩尔高等熵对应物相比，中熵非等摩尔CCFO表现出更低的热导率（k），同时保持高模量（E），从而实现更高的E / k比率。这些结果表明通过探索非等摩尔和/或中等熵组成的热绝缘但刚性CCC（MPCC）的新方向。