High-performance and low thermal conductivity in nano-layered Cu2Se prepared by a NaCl-flux method
High-performance and low thermal conductivity in nano-layered Cu2Se prepared by a NaCl-flux method
复制标题
氯化钠熔剂法制备高性能低导热纳米层状 Cu2Se
DOI：
10.1039/c9ce01258c
复制
发表时间：
2019
期刊：
影响因子：
3.1
通讯作者：
Deng Shukang
中科院分区：
文献类型：
--
作者：
Liu Wenting;Shen Lanxian;Shai Xuxia;Sun Luqi;Lu Jianhua;Chen Jiali;Ge Wen;Deng Shukang
在本研究中，基于 Cu2Se(NaCl)x（x = 1.5、2、2.5、3 和 3.5）的化学计量比，使用 NaCl 助熔剂方法成功生长了纳米层状 Cu2Se 高性能材料。 X射线衍射结果表明，当1.5≤x≤2.5时，样品具有α相结构，而当x≥3时，样品由β相和α相结构混合组成。电子探针微量分析结果表明，所有样品中几乎没有发现Na或Cl原子。同时，当1.5≤x≤2.5时，实际成分接近Cu2Se的标称成分，而当x≥3时，实际成分偏离标称成分。样品中Cu和Se原子的价态分别为+1和-2。透射电镜结果表明，采用氯化钠熔剂法制备的晶体具有良好的质量。场发射扫描电镜图像显示，采用氯化钠助熔剂法制备的样品具有堆叠的纳米层状结构，平均厚度约为110 nm。这些薄层状晶体具有多个晶界，可以有效地散射声子，从而导致超低的晶格热导率。 Cu2Se(NaCl)2.5 由于具有最低的热导率，因此在所有样品中表现出最好的热电性能。 700 K 时最大 ZT 值达到 1.42，远高于快速熔化淬火（700 K 时～0.88）、放电等离子烧结（700 K 时～0.8）和高温高压合成（700 K 时～1.13）制备的材料。
In this study, a nano-layered Cu2Se high-performance material is successfully grown using a NaCl-flux method based on the stoichiometric ratios of Cu2Se(NaCl)x (x = 1.5, 2, 2.5, 3, and 3.5). X-ray diffraction results show that samples possess an α-phase structure for 1.5 ≤ x ≤ 2.5, whereas samples consist of a mixture of β- and α-phase structures for x ≥ 3. Electron probe microanalysis results present that almost no Na or Cl atoms were found in all the samples. Meanwhile, the actual composition is close to the nominal composition of Cu2Se when 1.5 ≤ x ≤ 2.5, whereas it deviates from the nominal composition when x ≥ 3. The valence values of Cu and Se atoms are +1 and −2 in the sample, respectively. Transmission electron microscopy results prove that the crystals prepared using the NaCl-flux method have a good quality. The field emission scanning electron microscopy image shows that the samples prepared using the NaCl-flux method have a stacking nano-layered structure with an average thickness of approximately 110 nm. These thin lamellar crystals have several grain boundaries, which can effectively scatter the phonon and thus result in ultra-low lattice thermal conductivity. Cu2Se(NaCl)2.5 exhibits the best thermoelectric performance among all the samples because it has the lowest thermal conductivity. The maximum ZT value reaches 1.42 at 700 K, which is much higher than those prepared using fast melt-quenching (∼0.88 at 700 K), spark plasma sintering (∼0.8 at 700 K) and high-temperature and high-pressure synthesis (∼1.13 at 700 K).