Effects of Ti addition on properties of Sr2Nb2O7 thermoelectric ceramics

New thermoelectric ceramics Sr2Nb2−xTixO7 prepared by a reaction-sintering process were investigated. The calcinations and subsequent pulverization stages were bypassed. Dense Sr2Nb2O7 with 5.15 g cm−3 (97.9% of the theoretical density) was observed after 1400 °C/6 h sintering. Grain size decreased as Ti was doped into Sr2Nb2O7 ceramics. Resistivity of Sr2Nb2O7 is 3.07×108 Ω cm at 200 °C and decreased to 4.77×104 Ω cm at 700 °C. Activation energy Ea for Sr2Nb2O7 is 0.7 eV at 200–700 °C. Ea for Sr2Nb1.97Ti0.03O7 and Sr2Nb1.95Ti0.05O7 increased from 0.23–0.4 eV at 200–400 °C to 0.77 eV at 400–700 °C. For Sr2Nb2O7, Seebeck coefficient S=26.93 μV K−1 at 200 °C and increased to 57.15 μV K−1 at 500 °C. For Sr2Nb1.97Ti0.03O7, S=25.57 μV K−1 at 200 °C and it increased to 50.21 μV K−1 at 500 °C.