Crystal growth of a series of lithium garnets Ln3Li5Ta2O12 (Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

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We report the single crystal structures of a series of lanthanide containing tantalates, Ln3Li5Ta2O12 (Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln3Li5Ta2O12 were determined by single crystal X-ray diffraction, where the Li+ positions and Li+ site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3¯d" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; line-height: normal; font-size: 14.4px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">Ia3¯d (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) Å for La3Li5Ta2O12, Pr3Li5Ta2O12, and Nd3Li5Ta2O12, respectively. A UV–Vis diffuse reflectance spectrum of Nd3Li5Ta2O12 was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd3Li5Ta2O12, the impedance data were collected in air in the temperature range 300⩽T(°C)⩽500.