INVESTIGATION OF STRUCTURAL, ELECTRICAL, DIELECTRIC PROPERTIES OF MIXED AND TETRAGONAL GARNET PHASES OF 𝐋𝐢𝟕𝐋𝐚𝟑𝐙𝐫𝟐𝐎𝟏𝟐 (LLZO)

Abstract

In this study, two different phases of Li7La3Zr2O12 (LLZO) i.e mixed(tetragonal garnet and cubic) and tetragonal garnet has been synthesized using a solid-state reaction route at low sintering temperature and different sintering times. X-ray diffraction (XRD) analysis has been carried out to confirm the formation of a mixed phase of tetragonal garnet and cubic structure and tetragonal garnet. The structural, physico-chemical, electrical, and dielectric characterization of synthesized LLZO are performed. The average crystallite size and strain have been estimated from the XRD peaks analysis using the Williamson Hall method. Field Emission Scanning Electron Microscope (FE-SEM) micrographs reveal slightly agglomerated and dense layer-like staircase kind of morphology in the mixed-phase and sheet-like porous structure for the tetragonal garnet at the nanolevel. The impedance spectroscopy data has been recorded at various temperatures from 303 K to 373 K over a frequency range of 70 kHz to 5 MHz. The electrical analysis indicates that charges possess the classical hopping mechanism for conduction. A.C. activation energy of mixed and tetragonal garnet phase of LLZO has been observed at a lower frequency of 70 kHz and it is noticed nearly of same order (0.16 eV). Dielectric results show the presence of space charge polarization in the external electric field which consists of hopping polarization in the bulk and interfacial polarization (Maxwell-Wagner polarization) at the grain boundaries in both the phases. The strength of polarization is seen as greater in the tetragonal garnet phase of LLZO.