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

Abstract A novel high entropy (HE) rare earth monosilicate (Yb0.25Y0.25Lu0.25Er0.25)2SiO5 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)2SiO5 exhibits excellent phase stability and anisotropy in thermal expansion. The coefficients of thermal expansion (CTEs) in three crystallographic directions are: αa = (2.57 ± 0.07) ×10-6  K-1, αb = (8.07 ± 0.13) ×10-6  K-1, αc = (9.98 ± 0.10) ×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)2SiO5 is controlled on either metal or ceramic substrate.