Negative thermal expansion in Er 2W 3O 12 and Yb 2W 3O 12 by high temperature X-ray diffraction

Abstract

Negative thermal expansion in the orthorhombic members of A 2W 3O 12 (A = Er, Yb, Y and Lu) tungstates is measured by high temperature X-ray diffraction. Two new compounds showing contraction in this iso-structural series, Yb 2W 3O 12 and Er 2W 3O 12 are identified. Axial thermal expansion coefficients of Y 2W 3O 12, Er 2W 3O 12, Yb 2W 3O 12 and Lu 2W 3O 12 calculated from high temperature X-ray diffraction (473–1073 K) shows rare earth size effect. The linear thermal expansion coefficient decreases as the ‘A’ cation size increases and the thermal contraction along the b-axis becomes more negative.