Thermoelectric power of ${\mathrm{Tl}}_2$${\mathrm{Ba}}_2$${\mathrm{Ca}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$${\mathrm{Cu}}_2$${\mathrm{O}}_{8+\mathit{y}}$ (0≤x≤0.6) samples

We report the thermoelectric power (TEP) of ${\mathrm{Tl}}_2$ ${\mathrm{Ba}}_2$ ${\mathrm{Ca}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Y}}_{\mathit{x}}$ ${\mathrm{Cu}}_2$ ${\mathrm{O}}_{8+\mathit{y}}$ (x=0–0.6) samples as a function of temperature in the temperature range 77–300 K. For the x=0 sample (${\mathit{T}}_{\mathit{c}}$=85 K), the room-temperature value of the TEP is negative. For x>0, the TEP is positive and its magnitude increases with increasing x (decreasing carrier concentration). A comparative study of our results with that of other high-${\mathit{T}}_{\mathit{c}}$ systems shows that the room-temperature value of the TEP is almost zero for samples with ${\mathit{T}}_{\mathit{c}}$∼${\mathit{T}}_{\mathit{c}}^{\max }$. The results are analyzed with three different models.