Growth, optical and thermal properties of Yb, Tm:KLu(WO4)2

Single crystal of Yb, Tm:KLu(WO4)2 (Yb, Tm:KLuW) with the size of 47×32×15 mm3 has been grown by the top-seeded solution growth (TSSG) method. The absorption spectrum was measured at room temperature. The measured specific heat is lower than that of KGd(WO4)2 (0.502 J/g K) at 100 °C, but it is similar to that of Yb:KLuW (0.365 J/g K) at 90 °C. The measured mean linear coefficients of thermal expansion are αc=16.61×10−6 K−1, αc*=15.04×10−6 K−1, αa=11.91×10−6 K−1, αa*=11.50×10−6 K−1, αb=5.91×10−6 K−1. The thermal conductivity coefficients are 2.71, 2.60, 2.22, 3.32 and 3.14 W/mK at 30 °C along the a, a*, b, c* and c directions, respectively. The results indicate that the crystal has a large anisotropy. The large anisotropy indicated that we should heat or cool the crystal with the temperature changing at a lower speed.