Intergrowth and thermoelectric properties in the Bi-Ca-Co-O system

X. G. Luo; Y. C. Jing; H. Chen; X. H. Chen

doi:10.1016/j.jcrysgro.2007.07.037

paper

Intergrowth and thermoelectric properties in the Bi-Ca-Co-O system

arXiv:0707.2503 · doi:10.1016/j.jcrysgro.2007.07.037

Abstract

Single crystals of the Bi-Ca-Co-O system have been grown using the flux method with cooling from 900$\celsius$ and 950$\celsius$, respectively. The single crystals are characterized by transmission electron microscopy and X-ray diffraction. The misfit cobaltite [Ca $_{2}$ Bi $_{1.4}$ Co $_{0.6}$ O $_{4}$ ] $^{R S}$ [CoO $_{2}$ ] $_{1.69}$ single crystals with quadruple ( $n$ =4) rocksalt (RS) layer are achieved with cooling from 900$\celsius$. Such crystal exhibits room-temperature thermoelectric power (TEP) of 180 $μ$ V/K, much larger than that in Sr-based misfit cobaltites with quadruple RS layer. However, intergrowth of single crystals of quadruple ( $n$ =4) and triple ( $n$ =3) RS-type layer-based misfit cobaltites is observed with cooling from 950$\celsius$. Both of TEP and resistivity were obviously enhanced by the intergrowth compared to [Ca $_{2}$ Bi $_{1.4}$ Co $_{0.6}$ O $_{4}$ ] $^{R S}$ [CoO $_{2}$ ] $_{1.69}$ single crystal, while the power factor at room temperature remains unchanged.

8 pages, 7 figures. To be published in Journal of Crystal Growth