Detailed characterization of thermal expansion tensor in monoclinic KRe(WO4)2 (where Re = Gd, Y, Lu, Yb)

► Potassium (rare-earth) double tungstate KRe(WO4)2 (Re = Gd, Y, Lu, Yb). ► Measurement of thermal expansion coefficients along a1, b1, c1∗ and Nm, Ng axes. ► KLu(WO4)2 crystal is characterized by lower thermal expansion anisotropy. ► Calculation of athermal propagation directions at 1.06 μm for E || Nm and E || Np.