Study of the [formula omitted] ceramics by X-ray diffraction, dielectric and Raman spectroscopy

Abstract

X-ray diffraction, dielectric, pyroelectric and Raman spectroscopy properties of Na 1 − x Bi x Nb 1 − x Mn x O 3 ( x = 0.05 , 0.075, 0.10, 0.15, 0.20 and 0.30) lead-free ceramics were investigated. Structural properties are confirmed using the Rietveld method. The effect of cationic substitution of sodium by bismuth at the A site and niobium by manganese at the B site in the NaNbO 3 perovskite lattice on physical properties, were investigated. X-ray diffraction shows that the room temperature phase is orthorhombic with space group Pbma. The permittivity-vs-temperature plots, resulting from dielectric measurements carried out in the temperature range of −150 to 500 °C and the frequency range of 100 Hz to 100 kHz, show various remarkable shapes depending on Bi and Mn substitution and structural changes. The evolution of the dielectric permittivity as a function of temperature and frequency shows a classical ferroelectric character for 0.05 ≤ x ≤ 0.10 and a relaxor type behaviour for 0.15 ≤ x ≤ 0.30 . Raman spectroscopy measurements confirm the ferroelectric behaviour of the room temperature for 0.05 ≤ x ≤ 0.10 and indicate an increasing of disorder when x increases.