Sodium gadolinium tungstate NaGd(WO4)2: Growth, crystallography, and some physical properties

Pure, and Nd3+-doped NaGd(WO4)2 (NGW) single crystals, up to ∼85 mm long and ∼30 mm in diameter, have been grown using the Czochralski method. The Nd3+ segregation coefficient for growth along the [1 0 0] direction was 1.3±0.025. X-ray diffraction at room temperature established the lattice constants as: a=5.2483(2) Å and c=11.392(2) Å, for the tetragonal scheelite-like structure (space group I41/a), with two formula units in the unit cell. Inter-atomic distances and bond angles are also given. The thermal expansion coefficients were αa=11.6×10−6 /°C and αc=23.3×10−6 /°C, in the a and c directions, respectively. The Nd3+ absorption spectrum at around 800 nm for E⊥c polarization was measured with high resolution, providing a peak absorption cross-section of 2.6×10−20 cm2 at 800.8 nm.