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Lead-free ferroelectric materials with Electrocaloric Effect (ECE) and recoverable energy (W rec) represent a major breakthrough in the technological race for manufacturing low-cost and eco-friendly smart multifunctional devices. Here, guided by the benefits resulting from successive ferroelectric-ferroelectric (F–F) and ferroelectric-pseudo cubic (F-PC) transitions including broad operational temperature span, lead-free Ba 0·90 Ca 0·10 Zr 0·15 Ti 0·85 O 3 (BCZT) ferroelectric ceramic located near the phase convergence region was prepared using the conventional solid-state solution. In this study, the systematic investigation of structural and microstructural properties via X-Ray Powder Diffraction (XRPD), scanning electron microscopy (SEM), temperature-dependence Raman spectroscopy and dielectric properties confirm the formation of a pure perovskite material which undergoes consecutive R 3 c - R 3 m , R 3 m - Amm 2, Amm 2- P 4 mm (F–F) phase transitions followed by (F-PC) transition in a wide temperature range centered around room temperature (RT). Polarization-Electric field (P-E) measurements, revealed the coexistence of Positive Electro-Caloric Effect (PECE) and Negative Electro-Caloric Effect (NECE) in a wide temperature span of [-40 °C, 95 °C]. More interestingly, we reached a large absolute temperature change (ΔT) and EC coefficient (ξ) values of (5.505 °C, 1.847 KmmkV−1), (0.861 °C, 0.289 KmmkV−1) and (1.897 °C, 0.637 Kmm kV−1) registered respectively at about −5, 42.5 and 74.5 °C under an electric field of 29.80 kVcm−1. This work will promote further studies on lead-free BCZT ceramics towards multifunctional environmentally-friendly material promising for solid-state cooling technology. [ABSTRACT FROM AUTHOR]

Abstract: X-ray diffraction, dielectric, pyroelectric and Raman spectroscopy properties of (, 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 site and niobium by manganese at the 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 and a relaxor type behaviour for . Raman spectroscopy measurements confirm the ferroelectric behaviour of the room temperature for and indicate an increasing of disorder when increases. [Copyright &y& Elsevier]