CaGdAlO₄ (CGA) crystal with dimensions of Φ 30 × 30 mm³ was successfully grown by the Czochralski (CZ) method. The CaGdAlO₄ crystal belongs to an isostructural family of crystals with the general formula ABCO₄, where A denotes Ca or Sr, B represents rare-earth ion, C is Al or Ga. In this structure, the C exists in slightly distorted octahedral sites stacked in layers perpendicular to the c-direction. In the layers, the divalent A and trivalent B cations reside in ninefold coordinated sites which have distorted C_4v Symmetry due to the random occupation of neighbouring sites by Ca²⁺ and Gd^3+[1]. It is a promising host material for ultrafast laser due to its disorder structure and high thermal conductivity. 

    The crystal growth was carried out in State Key Laboratory of Crystal Materials, Shandong University. The raw materials, including CaCO₃ and Gd₂O₃, and Al₂O₃, were accurately weighed according to charges of stoichiometric composition and adequately mixed, and then pressed into tablets with dimensions of Φ 50 × 60 mm³. Afterwards, the tablets were sintered in air at 1350 °C for 45h before they were melted in an Ir crucible with a diameter of 60 mm and a height of 60 mm. An inert atmosphere of argon gas was adopted in order to prevent oxidation of the iridium crucible. After the crystal growth, a high quality CGA crystal along c-direction was grown.

    Single crystal X-ray analysis was carried out on a Bruker SMART APEX-II equipped with CCD area-detector diffractometer at 296 K using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) with the f and w scans method. In addition, thermal properties including thermal expansion, specific heat, thermal diffusivity and thermal conductivity were investigated as a function of temperature. The transmission spectra and refractive indices were also measured. 

References:

[1] Jon-Paul R Wells, Mitsuo Yamaga Nobuhiro Kodama andThomas P J Han

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1. Crystal growth of CaGdAlO₄ by Cz method
2. Growth and Properties of Mid-infrared Chalcogenide Crystals