Development of Na_0.5CoO₂ Thick Film Prepared by Screen-Printing Process

The Na_0.5Co_0.9Cu_0.1O₂ thick film with the same thermoelectric performance as a Na_0.5CoO₂ bulk was formed on an alumina substrate by the screen-printing process. The power factor exceeded 0.3 mW/K²m, with the resistivity of 3.8 mΩcm and the thermopower of 108 μV/K. The thick film without any cracks strongly adhered to the substrate. The high-quality thick film had been realized through the carefully designed and improved process, mixing NaCl to promote the anisotropic sintering of Na_0.5Co_0.9Cu_0.1O₂, inserting a CuO interlayer to adhere the film and substrate, and Co-Cu substituting Cu for Co to control the sintering temperature.