Growth, structure and thermal properties of Yb3+-doped NaGd(WO4)2 crystal

Yb3+ : NaGd(WO4)2 single crystal with dimensions O30 × 60 mm2 has been grown by the Czochralski method. XRPD experimental results show that the as-grown Yb3+ : NaGd(WO4)2 crystal belongs to the tetragonal system and the I41/a space group. The high crystalline quality of the as-grown Yb3+ : NaGd(WO4)2 crystals was confirmed by HRXRD. The effective segregation coefficient of the Yb element in Yb3+ : NaGd(WO4)2 crystal growth was measured to be 0.812 using the x-ray fluorescence method. Subsequently, the thermal properties were systematically studied by measuring the thermal expansion, specific heat and thermal diffusion coefficients. The density of the as-grown Yb3+ : NaGd(WO4)2 crystal at 22 °C was measured by using the buoyancy method with a resulting value of 7.143 g cm−3 and almost linearly decreases as the temperature increases due to the thermal expansion. Comparing the thermal properties of several tungstate crystals, we find that the Yb3+ : NaGd(WO4)2 crystal possesses relatively larger anisotropic thermal expansion and specific heat but smaller thermal conductivity than those of other tungstate crystals.