Structure, surface and broadband impedance spectroscopy of Li4Ti5O12 based ceramics with Nb and Ta

The structural investigation of the Li4Ti5O12 (LTO), Li4Ti4.95Nb0.05O12 (LTO + Nb) and Li4Ti4.95Ta0.05O12 (LTO + Ta) powders was conducted by X-ray diffraction (XRD) in temperature range (300-1270) K. These compounds have cubic spinel-type structure in the investigated temperature range. Ceramic samples were sintered for X-ray photoelectron spectroscopy (XPS) and impedance spectroscopy study. Binding energies of Ti 2p and O1s core levels XPS on the surfaces of the ceramics have been investigated at room temperature. Two and four probe voltmeter-ammeter methods were used for the measurements of electrical impedance in the frequency range 10 Hz-1 MHz. Coaxial waveguide technique was used for the investigation of impedance spectra in the frequency range from 1 MHz to 3 GHz. Electrical properties of the ceramics were studied in the temperature interval (300-780) K.