Microstructure and thermoelectric properties of Zn1−xAlxO ceramics fabricated by spark plasma sintering

Al-doped ZnO powders were synthesized via solid reaction between Zn(OH)2 and Al(OH)3 and consolidated by spark plasma sintering (SPS) to fabricate fine-grained Zn1−xAlxO ceramics as a thermoelectric material. X-ray diffraction and spectrophotometer experiments revealed that Al doping into ZnO is enhanced by the present process, and consequently the SPS-processed Zn1−xAlxO samples show significantly improved electrical conductivity as compared with those prepared via mixing ZnO and Al2O3 oxide powders. Because of the combined effect of Al doping and grain refinement, the present Zn1−xAlxO ceramics show much lower thermal conductivity, which also results in an enhanced dimensionless figure of merit (ZT), than un-doped ZnO oxides prepared also by SPS.