Correlation between micro-structural properties and ionic conductivity of Li1.5Al0.5Ge1.5(PO4)3 ceramics

• Published in: Journal of power sources 2011-08, Vol.196 (15), p.6456-6464
• Main Authors: Mariappan, Chinnasamy R., Yada, Chihiro, Rosciano, Fabio, Roling, Bernhard
• Format: Article
• Language: English
• Subjects: Applied sciences; Brick layer model; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Finite element approach; Flash creation method; Ionic conductivity; LAGP ceramics
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2011.03.065

▶ Li1.5Al0.5Ge1.5(PO4)3 ceramics were prepared from amorphous powders, which had been synthesized by the flash creation method. ▶ A maximum total conductivity of 2×10−4S/cm at room temperature was found for a sample sintered at 750°C for 2h. ▶ The classical brick layer model does not adequately describe the ion transport through the grain boundaries. ▶ The predictions of a finite-element approach taking into account the limited contact area between the grains are in good agreement with the experimental ratio of grain and grain boundary resistance. We report on the structure and lithium ion transport properties of Li1.5Al0.5Ge1.5(PO4)3 (LAGP). This material is commercially available and is prepared as amorphous powders via a flame spray technique called Flash Creation Method (FCM). We crystallize and sinter the amorphous powders at different temperatures in order to alter grain size and grain boundary properties. The structure is then characterized by means of powder X-ray diffraction, atomic force microscopy, scanning electron microscopy and transmission electron microscopy with energy dispersive X-ray spectroscopy. AC impedance spectroscopy is used to study lithium ion transport. A maximum total conductivity of 2×10−4Scm−1 at room temperature is found for a sample sintered at 750°C for 2h. In order to distinguish between grain and grain boundary contributions to the impedance spectra, equivalent circuit fits are carried out. The results are analysed in the framework of the classical brick layer model and of a finite-element approach taking into account non-ideal grain contacts. Our experimental results for the grain and grain boundary resistances are in good agreement with the predications of the finite-element approach.