TY - JOUR
T1 - Effects of preferred orientation and crystal size on thermoelectric properties of sodium cobalt oxide
AU - Wu, Yin
AU - Wang, Jun
AU - Yaer, Xinba
AU - Miao, Lei
AU - Zhang, Boyu
AU - Guo, Feng
AU - Zhang, Shuai
N1 - Publisher Copyright:
© 2016 World Scientific Publishing Company.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - To examine the effect of crystal size and orientation effect on ZT, polycrystalline NaxCo2O4 materials were prepared by pressing layered crystals obtained in sol-gel (SG) synthesis, molten salt synthesis (MSS) with and without additional ball milling (BM) treatment and 1:1 molar ratio mixture (Mixture) of BM powder and MSS powders. We found that the orientation effect and crystal size for four samples follow Mixture < SG < BM < MSS and BM < Mixture < SG < MSS, respectively. Electrical conductivity was obviously enhanced in the highly orientated BM and MSS samples when compared with SG and Mixture. It appears that the crystal size plays a dominant role in thermal conductivity rather than Seebeck coefficient by controlling the phonon scattering at grain boundaries. Thermal conductivity for BM was significantly decreased in comparison to MSS, although both BM and MSS show comparable orientation effect. The maximum ZT value is developed to near 0.51 at 814K upon increasing the electrical resistivity and decreasing the thermal conductivity, which are mainly governed by the condition of crystal size and orientation effect.
AB - To examine the effect of crystal size and orientation effect on ZT, polycrystalline NaxCo2O4 materials were prepared by pressing layered crystals obtained in sol-gel (SG) synthesis, molten salt synthesis (MSS) with and without additional ball milling (BM) treatment and 1:1 molar ratio mixture (Mixture) of BM powder and MSS powders. We found that the orientation effect and crystal size for four samples follow Mixture < SG < BM < MSS and BM < Mixture < SG < MSS, respectively. Electrical conductivity was obviously enhanced in the highly orientated BM and MSS samples when compared with SG and Mixture. It appears that the crystal size plays a dominant role in thermal conductivity rather than Seebeck coefficient by controlling the phonon scattering at grain boundaries. Thermal conductivity for BM was significantly decreased in comparison to MSS, although both BM and MSS show comparable orientation effect. The maximum ZT value is developed to near 0.51 at 814K upon increasing the electrical resistivity and decreasing the thermal conductivity, which are mainly governed by the condition of crystal size and orientation effect.
KW - Thermoelectric
KW - molten salt synthesis
KW - preferred orientation
KW - sodium cobalt oxide
KW - sol-gel method
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U2 - 10.1142/S1793604716500107
DO - 10.1142/S1793604716500107
M3 - Article
AN - SCOPUS:84960376534
VL - 9
JO - Functional Materials Letters
JF - Functional Materials Letters
SN - 1793-6047
IS - 1
M1 - 1650010
ER -