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The polycrystalline sample of a double perovskite, Sm 2 NiMnO 6 was synthesized by a solid-state reaction route. From the X-ray structural study, it is found that the structure of the material is monoclinic with lattice parameters: a = 4.1750(63) Å, b = 7.6113(63) Å, c = 5.9896(63) Å, and β = 112.70°. These parameters are very close to and consistent with those of such type of materials. The dielectric, impedance, AC conductivity, and electrical modulus properties of the sample were studied in the temperature range of 25-300 ℃ and the frequency range of 1 kHz-1 MHz. Typical relaxor behavior observed in the dielectric studies was confirmed by Vogel-Fulcher fitting. From the Nyquist plots, the temperature dependent contribution of grain and grain boundary effect was confirmed. The non-Debye type of relaxation was found using the complex impedance spectroscopy. The magnetic study revealed that the sample had paramagnetic behavior at room temperature. Magneto-electric (ME) coefficient was obtained by changing DC bias magnetic field. This type of lead-free relaxor ferroelectric compound may be useful for high-temperature applications.

In this paper, dielectric relaxor, impedance, AC conductivity and electrical modulus of double perovskite Nd 2 NiMnO 6 , prepared by a solid state reaction method and sintered at 1250°C, have been reported in the wide temperature (25-150°C) and frequency (1 kHz-1 MHz) ranges. From the preliminary X-ray structural analysis, it is found that the structure of the material is monoclinic. In the study of the temperature dependence of the dielectric constant, the relaxor behaviour of the material is observed. Such type of behaviour is explained by a modified Curie-Weiss and a Vogel-Fulcher law. By analysing Nyquist plots, the existence of grain and grain boundary effects is established. The non-Debye type of relaxation is investigated by the analysis of complex impedance and the modulus data. From the study of impedance data, it is found that the grain resistance is reduced with the increase in temperature indicating the existence of negative temperature coefficient of resistance (NTCR) behaviour in the material which also matches with temperature versus AC conductivity plots. From these results, it may be concluded that this compound may have extreme potential for different high temperature applications.