Sodium gadolinium tungstate NaGd(WO_4)_2: Growth, crystallography, and some physical properties

摘要

Pure, and Nd~(3+)-doped NaGd(WO_4)_2 (NGW) single crystals, up to ～85mm long and ～30mm in diameter, have been grown using the Czochralski method. The Nd~(3+) segregation coefficient for growth along the [100] direction was 1.3±0.025. X-ray diffraction at room temperature established the lattice constants as: a = 5.2483(2) A and c = 11.392(2) A, for the tetragonal scheelite-like structure (space group I4_1/a), with two formula units in the unit cell. Inter-atomic distances and bond angles are also given. The thermal expansion coefficients were α_a = 11.6 x 10~(-6)/℃ and α_c = 23.3 x 10~(-6)/℃, in the a and c directions, respectively. The Nd~(3+) absorption spectrum at around 800 nm for E⊥c polarization was measured with high resolution, providing a peak absorption cross-section of 2.6 x 10~(-20)cm~2 at 800.8 nm.