<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Ln(IO<sub>3</sub>)<sub>3</sub> (Ln = Ce, Nd, Eu, Gd, Er, Yb) polycrystals are hydrothermally prepared using aqueous solutions of Ln(NO<sub>3</sub>)<sub>3</sub> or Ln<sub>2</sub>O<sub>3</sub> and HI as precursors (autoclave, 230 °C, 24 h).</p> </abstract>