Abnormal thermal expansion coefficients in (Nd _{1− <i>x</i>}Dy _<i>x</i>) ₂Zr ₂O ₇ pyrochlore: The effect of low-lying optical phonons

Chemical doping is a normal strategy to tune thermal expansion coefficient (TEC) of ceramics in engineering applications, but the resultant TEC values usually follow Vegard’s law, as does not modify nature chemical bonding and its anharmonicity. In this paper, we report abnormal behavior (Nd1−xDyx)2Zr2O7 ceramics, where remarkably exceed predicted by law even obtained for two constituents Nd2Zr2O7 Dy2Zr2O7. addition reduction lattice energy with an increasing molar fraction Dy (x) value, attribute additional increase high concentration dopants pyrochlore (P) region, which can soften low-lying optical phonon modes induce strongly avoided crossing acoustic branches enhanced We believe that finding provide new route break through restriction imposed conventional on bring opportunities barrier coatings (TBCs) or ceramic/metal composites towards realizing minimized mismatch prolonged service life during cycling.