Synthesis, structural and electrochemical properties of new ytterbium-doped langbeinite ceramics

In this work we have successfully synthesized highly pure phases of K2Mg2(SO4)3:xYb3+(x=0.2, 0.5 and 1 mol%) langbeinite powders denoted as KMgYbx (x=0.2, 0.5 and 1) using the solid-state reaction method. Structural characterization was carried out via the Rietveld method on the X-ray powder diffraction data and the results confirmed that the Yb3+ dopant can replace the magnesium in this structure with a slight increase of the lattice parameters. The electrical conductivity was studied by impedance spectroscopy in the [633-7237 K] temperature range and results show that the undoped sample was a low ionic solid electrolyte conductor. The doped materials show a semiconductor ionic character and the conductivity of K2Mg2(SO4)3:xYb3+ decreases when the Yb3+ dopant content x is increased. Results also show that K2Mg2(SO4)3:0.2Yb3+ has the highest electrical conductivity. It has therefore been concluded that doping with the appropriate amount of ytterbium trivalent and obtaining denser materials sintered at 1073 K can further improve the electrical properties of langbeinite.