Tetragonal Li7La3Zr2O12 (LLZ) was synthesised by the solid-state and citrate–nitrate methods. The crystal structure of the samples was characterised by the X-ray diffraction method. The morphology of the particles was investigated using both optical microscopy and a particle size analysis method. The ceramic samples were studied by complex impedance spectroscopy in the frequency range from 12 to 105 Hz, in the temperature range of 20–400°C. Synthesis by the citrate–nitrate method makes it possible to reduce both the temperature and time of the synthesis and also prepare the product with smaller particles. The conductivity of LLZ synthesised by the citrate–nitrate method (5.2×10−6 Scm−1 at 20°C) is higher than the conductivity of LLZ synthesised by the solid-state method (1.3×10−6 Scm−1 at 20°C).