Overview of spark plasma texturing of functional ceramics

Abstract

This work reports the progress in the preparation of superconducting and thermoelectric lamellar compounds processed by the unconventional Spark Plasma Sintering (SPS). The SPS equipment was modified with the aim of obtaining the textured and dense superconductor Bi2 Sr2 Ca2 Cu3 O10, p-type oxide thermoelectric bulk as Ca3 Co4 O9 and Ca3-x Agx Co4 O9 /Ag composites respectively. The new process is referred to as Spark Plasma Texturing (SPT). During SPT, the bulk material can freely deform. As a result, inter-grain preferential crystallographic orientation is created. The series of sintered and textured samples using the same Ag content were processed respectively. From the results, we can evidence: (i) the magnetic and/or structural transition around 350◦ C, for both series of samples. (ii) The electrical resistivity (ρ) decreases with increasing Ag-substituted or Ag-added. (iii) The Seebeck coefficient (S) of the textured series is higher than that of the sintered series. In the case of the Ag-substituted, S, decreases with Ag content. The optimized composite is found to be Ca2.6 Ag0.4 Co4 O9 /8wt% Ag. We can note the remarkable reduction of ρ, and the improvement of power factor values up to 360 µW.m−1.K−2.The superconducting properties of single phased Bi2 Sr2 Ca2 Cu3 O10 (Bi2223) consolidated using SPS and SPT will also be discussed.