Conduction with Large Transport Entropy in Electrically Conducting Oxides and Its Applications to Thermoelectric Materials

我们在金属氧化物中对金属氧化物的特定形态进行了研究，并对它们的热电性质进行了研究。摘要如下所示：1.Ni揭示了NaCo_2O_4中的Na和Co的选择性替代物，即用于Codecreased the Seebeck coefficient的替代物。这些结果建议，即Ni在钴原子之间传播自旋-自旋交换，如果认为它对Oxide.2.2.Layered Vanadate LiV_2O_4和LiVO_2的分层晶体结构类似于NaCo_2O_4显示出较大的正热功率和更低的电条件。Attempted p-type doping failed to increase the conductivity， probably due to the large electron specific heat of the oxide observed to those observed for“heavy-fermion”materials，sugggesting large transport entropy in these oxides.3.Large enhancement of thermopower was observed for oxide materials with nanoviod structure。纳米氧化物结构是由150纳米的混合聚合物珠子组成的，直径为空心成形剂（VFA），并与启动氧化物粉末混合物一起制造，随后由在一个容器大气层中发射。结果的交错样品的电作用几乎与没有VFA的初级样品相同，但在500 -600-C左右，热力发电机显示出密集的负面最大值。这种热剂的增强作用可以被归因于氧化物中的多孔结构。Moreover，纳米材料样本的热行为显示出了一个有标记的降解率，从房间温度上升到760℃，这些结果强烈推荐纳米材料结构作为选择性散射中心的服务。

We have investigated large transport entropy in metal oxides with particular emphasis on their thermoelectric properties. The summary is as follows:1.Selective substitution for Na and Co in NaCo_2O_4 by Ni revealed that the substitution for Na decreased the electrical conductivity, whereas that for Co decreased the Seebeck coefficient. These results suggest that Ni at the Co sites disturbs the spin-spin exchange between the Co atoms, which has been considered to be responsible for unusually large thermopower of the oxide.2.Layered vanadate LiV_2O_4 and LiVO_2 with the layered crystal structure similar to that of NaCo_2O_4 showed large positive thermopower and rather low electrical conductivity. Attempted p-type doping failed to increase the conductivity, probably due to the large electron specific heat of the oxide comparable to those observed for"heavy-fermion" materials, suggesting large transport entropy in these oxides.3.Large enhancement of thermopower was observed for oxide materials with nanoviod structure. The nanovoid structure was induced by mixing polymer beads of 150 nm in diameter as a void forming agent (VFA) with the starting oxide powder mixture, followed by firing in an inert atmosphere. The electrical conductivity of the resulting sintered samples was almost the same as that of the pristine sample without VFA, yet the thermopower showed intense negative maxima at around 5 00-600 ーC. This enhancement of the thermopower can be attributed to the porous structure in oxides. Moreover, the thermal conductivity of the nanovoid samples showed a marked decrease by 30-35% from room temperature up to 760℃ These results strongly suggest that the nanovoid structure serves as selective scattering centers for phonons.