The influence of Al dopant on the structure, densification behavior and electrical conductivity of heavily doped Sm^sub 2^Ti^sub 2^O^sub 7

Powders with compositions Sm2Ti2-xAlxO7-δ (x = 0, 0.1, 0.2) were synthesized using a modified Pechini method. Thermal treatment at 1173 K leads to the formation of pyrochlore structure, together with other secondary phases. A decrease in linear shrinkage and shrinkage rate after partial substitution of titanium with aluminum was evidenced by dilatometry. Mainly pyrochlore phase was obtained for Sm2Ti2O7 and Sm2Ti1.9Al0.1O7-δ after thermal treatment at 1300 °C, while Al2TiO5 secondary phase was evidenced in Sm2Ti1.8Al0.2O7-δ pellet. Moreover, the addition of aluminum leads to the decrease in grain size and the presence of Al2TiO5 determine microcracks formation. The electrical conductivity of the single-phase samples was evaluated using EIS measurements. Al-doped sample exhibited higher conductivity and lower activation energy of conduction than undoped sample over the entire investigated temperature range for both bulk and grain boundaries components.