OPTIMIZATION OF FUNCTIONAL PROPERTIES OF La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> OXIDE-ION CONDUCTOR BY HETEROGENEOUS DOPING
Сomplex oxides La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> and La<sub>2</sub>Mo<sub>3</sub>O<sub>12</sub> were obtained by conventional solid-state reaction method. The { 0.9 La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>- 0.1 La<sub>2</sub>Mo<sub>3</sub>O<sub>12</sub>} composite was obtained by mechanical mixing of components. The phase composition of products was monitored by means of X-ray phase analysis. Transport properties, thermodynamic stability of matrix and composite samples were investigated. It has been established that introduction of an inert heterogeneous dopant La<sub>2</sub>Mo<sub>3</sub>O<sub>12</sub>, contributes to increase in conductivity of composite by 6-10 times relative to matrix sample, a decrease in the activation energy of conductivity, and an increase in the stability of ceramics at low partial oxygen pressures. However, it doesn`t suppress structural phase transition α-La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>→β-La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub>. The growth effect in conductivity of composite may be associated with partial stabilization of high-symmetry β-form La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> at low temperatures. The calculated activation energies of conductivity E<sub>a</sub> for La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> are 0.62 and 1.18 eV, respectively, at high and low temperatures. Values of E<sub>a</sub> are 0.53 and 1.12 eV, respectively, for composite. La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> is an ionic conductor in a wide range of oxygen partial pressures of 10<sup>-18</sup>-0.21 atm, contribution of electronic conductivity is absent up to 10<sup>-20</sup> atm for composite.