Dilatometric studies of $Y_2W_3O_{12}$ with added $Al_2O_3$

$Y_2W_3O_{12}$ exhibits negative thermal expansion along the three crystallographic directions due to the transverse thermal vibrations perpendicular to the Y–O–W linkage. It is highly hygroscopic and forms a trihydrate structure at room temperature. Dilatometric studies of $Y_2W_3O_{12}$ show large thermal expansion hysteresis due to large grain size and a large initial positive thermal expansion due to the removal of water molecules. $Al_2O_3$ has been added to $Y_2W_3O_{12}$ up to 10 wt% in an attempt to overcome the hygroscopicity and reduce the particle size and thereby the thermal expansion hysteresis. Thermo gravimetric, dilatometric and electron microscopic studies are presented to support these observations