Study of the Na1−xBixNb1−xMnxO3 ceramics by X-ray diffraction, dielectric and Raman spectroscopy

X-ray diffraction, dielectric, pyroelectric and Raman spectroscopy properties of Na1−xBixNb1−xMnxO3 (x=0.05x=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 AA site and niobium by manganese at the BB site in the NaNbO3 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≤0.100.05≤x≤0.10 and a relaxor type behaviour for 0.15≤x≤0.300.15≤x≤0.30. Raman spectroscopy measurements confirm the ferroelectric behaviour of the room temperature for 0.05≤x≤0.100.05≤x≤0.10 and indicate an increasing of disorder when xx increases.

► NNBM 0.05≤x≤0.30.05≤x≤0.3 occur at room temperature in orthorhombic phase and PbmaPbma space group.
► NNBM ceramic is a classical ferroelectric for 0.05≤x≤0.10.05≤x≤0.1 and a relaxor for 0.15≤x≤0.30.15≤x≤0.3.
► Pyroelectric properties for x=0.075x=0.075 and 0.2 ceramics confirm the dielectric results.
► The Raman confirms the ferroelectric behaviour of the room temperature for 0.05≤x≤0.10.05≤x≤0.1.
► Raman measurements show increase in disorder with increasing xx in the NNBM ceramics.