Spark plasma versus conventional sintering in the electrical properties of Nasicon-type materials

Abstract

Li_(1+x)M_(x)Ti_(2−x)(PO_(4))_(3) powders with x = 0 and 0.3 and M = Al, Cr and Fe have been sintered by conventional sintering (CS) and Spark Plasma Sintering (SPS), and the electrical properties have been compared. The use of SPS allows preparing samples with higher density at lower temperature and shorter time than the CS, avoiding segregation of secondary phases and with reduced crystallite size. The introduction of aluminum, chromium and iron in the LiTi_(2)(PO_(4))_(3) (LTP) clearly enhances ionic conductivity even if the samples have similar densities. Despite the different level of density reached with CS and SPS, the activation energies of dc and grain boundary contributions are very similar and the differences in ionic conductivity are determined by pre-exponential factors. The samples produced by SPS showed a well-defined grain boundary meaning a more homogenous electrical contact.