Ionic Conductivity of KMgCr(MoO4)3 Molybdate

The ionic conductivity sigma of KMgCr(MoO4)(3) crystal has been investigated in a temperature range of 575-932 K by impedance spectroscopy in the frequency range of (5-5) x 10(5) Hz. Ternary molybdate was obtained from the initial MgMoO4 and KCr(MoO4)(2) reagents by solid-phase technique in air at 923-973 K for 200 h. The temperature dependence sigma(T) of a ceramic sample exhibits a jump of sigma by a factor of about 4 at 833 +/- 5 K, which is caused by the first-order phase transition. The sigma value above the phase-transition temperature reaches 6 x 10(-4) S/cm (932 K) at an ion-transport activation enthalpy of 0.84 +/- 0.05 eV. The most likely carriers in KMgCr(MoO4)(3) are K+ cations.