Thermoelectric properties of Ca3−xEuxCo4O9+δ (0≤x≤0.1)

Effects of Eu and Fe co-doping on thermoelectric properties of misfit-layered Ca3Co4O9+δ

“…Thus, the electrical resistivity increases. Similar results were also reported by some groups [11][12][13][14][15][16]28]. As for the x = 0.1 and y = 0.1 sample, its semiconducting-like character is clear at measured temperature.…”

“…On the basis of the previously reported data, the substitution of Eu for Ca can increase thermopower and electrical resistivity, which could be attributed to the decrease of the hole (Co 4? ) concentrations, and suppresses the thermal conductivity [12,28]. On the other hand, the Fe substitution at Co-site could enhance the thermopower and decrease the electrical resistivity, which is believed to be associated with the increased carrier concentration and the enhanced electronic correlations [7,19].…”

Improving thermoelectric properties of Ca3Co4O9+δ through both Na doping and K addition at optimal values

“…Therefore, thermoelectric (TE) materials, that have the capability of converting heat differences directly to electricity, can play a key role in applications for On the other hand, in spite of the relatively low TE performances of oxide materials, they can be improved by both doping using appropriate chemical elements such as Ag, Eu, Zr, or Ti [1][2][3][4][5][6][7] and fabrication methods in their preparation, such as hot pressing, spark plasma sintering, or laser floating zone [8][9][10][11][12]. It can be generally expected that the partial substitution of cations in electroceramic materials such as thermoelectrics and superconductors can provide useful changes in the carrier concentration, while optimizations in material preparation methods ensure higher grain orientation to provide the enhancement of electrical conductivity.…”

High temperature thermoelectric properties of co-doped Ca3−xAgxCo3.95Fe0.05O9+δ (0≤x≤0.3)

“…Many attempts have been made to optimize the thermoelectric performance of Ca 3 Co 4 O 9 þ δ by either partially substituting cations or using appropriate fabrication methods such as hot pressing (HP) or spark plasma sintering (SPS) techniques. Partial replacement of cations in Ca 3 Co 4 O 9 þ δ has been carried out on either the Ca site [7,8] or the Co sites [9,10]. It has been reported that partial substitution for Ca by heavier ions with trivalence such as Eu 3 þ [7], Nd 3 þ [11], Bi 3 þ [5], Gd 3 þ [12] and Yb 3 þ [13], is effective in improving thermoelectric properties.…”

“…Partial replacement of cations in Ca 3 Co 4 O 9 þ δ has been carried out on either the Ca site [7,8] or the Co sites [9,10]. It has been reported that partial substitution for Ca by heavier ions with trivalence such as Eu 3 þ [7], Nd 3 þ [11], Bi 3 þ [5], Gd 3 þ [12] and Yb 3 þ [13], is effective in improving thermoelectric properties. Besides, the monovalent silver ion substitution on the Ca site has been found to reduce electrical resistivity and increase thermopower simultaneously, which in turn results in power factor enhancement [14][15].…”