High entropy (Yb0.25Y0.25Lu0.25Er0.25)2SiO5 with strong anisotropy in thermal expansion

A novel high entropy (HE) rare earth monosilicate (Yb0.25Y0.25Lu0.25Er0.25)(2)SiO5 was synthesized by solid-state reaction method. X-ray diffraction and scanning electron microscopy analysis indicate that a single solid solution is formed with homogeneous distribution of rare-earth elements. HE (Yb0.25Y0.25Lu0.25Er0.25)(2)SiO5 exhibits excellent phase stability and anisotropy in thermal expansion. The coefficients of thermal expansion (CTEs) in three crystallographic directions are: alpha(a) = (2.57 +/- 0.07) x 10(-6) K-1, alpha(b) = (8.07 +/- 0.13) x 10(-6) K-1, alpha(c) = (9.98 +/- 0.10) x 10(-6) K-1. The strong anisotropy in thermal expansion is favorable in minimizing the coating/substrate mismatch if preferred orientation of HE (Yb0.25Y0.25Lu0.25Er0.25)(2)SiO5 is controlled on either metal or ceramic substrate. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.