Synthesis of Ca-Co hydroxides and their use in facile fabrication of textured CayCoO2 thermoelectric ceramics
Synthesis of Ca-Co hydroxides and their use in facile fabrication of textured CayCoO2 thermoelectric ceramics
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Ca-Co氢氧化物的合成及其在织构化CayCoO2热电陶瓷的简易制造中的应用
DOI：
10.1016/j.ceramint.2018.11.020
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发表时间：
2019
影响因子：
5.2
通讯作者：
Fujihara Shinobu
中科院分区：
文献类型：
--
作者：
Shimonishi Rina;Hagiwara Manabu;Fujihara Shinobu
合成了钙含量较高的水镁石型氢氧化物CaZCo1−z(OH)2，并将其作为制备半导体层状钙钴氧化物CaCoO2块体陶瓷的单一前驱体。以氢氧化钾为碱源，采用反相共沉淀法成功地获得了高达0.22的片状CaCo1-−-z(OH)2颗粒。片状CaZCo1−z(OH)2(z= 0.2 2)经373K K预烧后，在高达5 0 0 Mpa的压力下进行单轴压制，可得到高度致密的绿色颗粒，沿压制方向呈片状堆积。然后在923 K下进行热处理，通过类似拓扑定向的热解反应将生球转化为(010)择优取向的CoO6八面体氧化物陶瓷。虽然陶瓷中还含有少量的绝缘Co3O4相(热分析估计为16.7 ± 0.7 %)，但电学测量证实了陶瓷的ITSP型半导体行为是由CaCoO2相引起的，室温下塞贝克系数超过160μV/K。
A brucite-type hydroxide of CazCo1−z(OH)2with a high Ca content was synthesized and utilized as a single-source precursor for the fabrication of bulk ceramics of a semiconducting layered calcium cobaltite CayCoO2. Plate-like CazCo1−z(OH)2particles withzup to 0.22 were reproducibly obtained by a reverse co-precipitation method using KOH as an alkaline source. Uniaxial pressing of the plate-like CazCo1−z(OH)2particles (z= 0.22), which was calcined at 373 K beforehand, at a pressure as high as 500 MPa produced a highly dense green pellet where the plate-like particles were stacked along the pressing direction. The green pellet was then converted by a heat treatment at 923 K into an oxide ceramic of preferentially (010)-oriented CayCoO2via a topotactic-like pyrolytic reaction maintaining edge-sharing CoO6octahedra. Although the ceramic also contained a minor insulating Co3O4phase (16.7 ± 0.7 mol% estimated from thermal analysis), the electrical measurements proved itsp-type semiconducting behavior resulting from the CayCoO2phase with enhanced Seebeck coefficient exceeding 160 μV/K at room temperature.