Negative thermal expansion in Er2W3O12 and Yb2W3O12 by high temperature X-ray diffraction

Negative thermal expansion in the orthorhombic members of A2W3O12 (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, Yb2W3O12 and Er2W3O12 are identified. Axial thermal expansion coefficients of Y2W3O12, Er2W3O12, Yb2W3O12 and Lu2W3O12 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.