Tunable thermal expansion and magnetism in Zr-doped ScF₃

The negative thermal expansion (NTE) behavior provides us an opportunity to design materials with controllable coefficient of thermal expansion (CTE). In this letter, we report a tunable isotropic thermal expansion in the cubic (Sc_{1- x}Zr_x)F_{3+ δ} over a wide temperature and CTE range (α_l = -4.0 to+ 16.8 × 10^-6 K^-1, 298-648 K). The thermal expansion can be well adjusted from strong negative to zero, and finally to large positive. Intriguingly, isotropic zero thermal expansion (α_l = 2.6 × 10^-7 K^-1, 298-648 K) has been observed in the composition of (Sc_0.8Zr_0.2)F_{3+ δ}. The controllable thermal expansion in (Sc_{1- x}Zr_x)F_{3+ δ} is correlated to the local structural distortion. Interestingly, the ordered magnetic behavior has been found in the zero thermal expansion compound of (Sc_0.8Zr_0.2)F_{3+ δ} at room temperature, which presumably correlates with the unpaired electron of the lower chemical valence of Zr cation. The present study provides a useful reference to control the thermal expansion and explore the multi-functionalization for NTE materials.