Synthesis, Consolidation and Significant Enhancement in Thermoelectric Properties of \(Ca_3Co_4O_9\) Bulk Ceramics by Adding Silver Combine Spark Plasma Texturing

Abstract

The objective of this work is the significant enhancement of the thermoelectric properties of Ca₃Co₄O₉ bulk ceramic by an innovative process ‘Spark plasma Texturing’ (SPT) able to integred into thermoelectric device. The work consisted in synthesizing Ca₃Co₄O₉ compound by substituting Ca²⁺ cations with Ag⁺ cations, or by adding massive silver in the Ca3Co4O9 phase in order to take advantage of the metallic nature of silver and the effect of texture to optimize the power factor (PF) and the figure of merit (ZT). The thermoelectric performance (for either power generation or cooling) depends on the efficiency of the thermoelectric material for transforming heat into electricity. The efficiency of a thermoelectric material depends primarily on the thermoelectric materials figure-of-merit, known as zT (0). The XRD data have shown that major phase is the Ca₃Co₄O₉ one, accompanied by metallic Ag phase, which shows that Ca₃Co₄O_9//Ag compound is composite.  Both the traditional way of synthesizing reaction in the solid state and the cutting-edge texturing approach known as Spark Plasma Texturing (SPT), which combines the directed nature of Hot Pressing (HP) and the Spark Plasma Sintering (SPS) method, were utilized. Grain sizes and preferred orientation perpendicular to the pressing axis are revealed by microstructural examination of sintered pellets produced by SPT. These grains are considerably bigger in size than those produced by SPS. Consequently, the study obtained a maximum PF value 555\(\mu\)W.m^-1K^-2 at , which is among the best reported about textured materials and a time saving of  98% compared to Hot Pressing (HP).