Synthesis, structure and ionic conductivity in scheelite type Li_0.5Ce_0.5-xLn_xMoO₄ (x = 0 and 0.25, Ln = Pr, Sm)

Abstract

Scheelite type solid electrolytes, Li_0.5Ce_0.5-xLn_xMoO₄ (x = 0 and 0.25, Ln = Pr, Sm) have been synthesized using a solid state method. Their structure and ionic conductivity (σ) were obtained by single crystal X-ray diffraction and ac-impedance spectroscopy, respectively. X-ray diffraction studies reveal a space group of I4₁/a for Li_0.5Ce_0.5-xLn_xMoO₄ (x = 0 and 0.25, Ln = Pr, Sm) scheelite compounds. The unsubstituted Li_0.5Ce_0.5-xLn_xMoO₄ showed lithium ion conductivity ∼10⁻⁵-10⁻³ Ω⁻¹cm⁻¹ in the temperature range of 300-700°C (σ = 2.5 × 10⁻³ Ω⁻¹cm⁻¹ at 700°C). The substituted compounds show lower conductivity compared to the unsubstituted compound, with the magnitude of ionic conductivity being two (in the high temperature regime) to one order (in the low temperature regime) lower than the unsubstituted compound. Since these scheelite type structures show significant conductivity, the series of compounds could serve in high temperature lithium battery operations.