Structure, crystal growth and physical anisotropy of KYb(WO₄)₂, a new laser matrix

Abstract

The crystal structure of monoclinic KYb(WO 4 ) 2 (KYbW) crystals has been refined (in space group C 2/ c ) at room temperature by using single-crystal X-ray diffraction data. KYbW undoped crystals were grown by the TSSG (top-seeded-solution growth) slow-cooling method. The crystals show {110}, {\bar{1}11}, {010} and {310} faces, which basically define their habit. The linear thermal expansion tensor has been determined and the principal axis with maximum thermal expansion (\alpha ^{\,\prime}_{33} = 16.68 × 10 −6 K −1 ), {\bf X}^{\,\prime}_{3}, was located 12° from the c axis. Its principal {\bf X}^{\,\prime}_{1}, {\bf X}^{\,\prime}_{2} and {\bf X}^{\,\prime}_{3} axes are [302], [010] and [106] directions, respectively, in the crystallographic system. The optical tensor has been studied at λ = 632.8 nm at room temperature; two principal axes, N g and N m , are located in the a c plane, while the other, N p , is parallel to [010]. The principal axis with maximum refractive index ( n g = 2.45), N g , was located 19° from the c axis.