研究目的
Investigating the dielectric, electrical, and impedance properties of the multiferroic material Pb(Ni1/3Mn1/3W1/3)O3 for multifunctional applications.
研究成果
The multiferroic Pb(Ni1/3Mn1/3W1/3)O3 is prepared by the solid-state reaction route at the moderate temperature. The orthorhombic crystal system has been suggested for the PNMW material using the observed re?ections in the X-ray diffraction patterns. The material undergoes a relaxation process (thermally activated) due to the dominance of the charge carriers following the hopping mechanism. The temperature dependence of dielectric constant plot veri?es the formation of single-phase transitions below 600 K; the ?rst transition Tc appeared at 457 K. The Nyquist plots were modelled with an equivalent circuit (CQR) (CR), and the respective parameters such as bulk/grain, resistance of boundary of grain resistance and capacitance were also reported. The bulk resistance (Rb) decreases signi?cantly as the temperature is increased from 298 to 573 K which justi?es exhibiting the negative temperature of resistance (NCTR).
研究不足
The presence of small extra phases in the PNMW due to the reaction between PbO and WO3 to form PbWO4 in the temperature range of 1023–1123 K, which may affect the material's properties.
1：Experimental Design and Method Selection:
The multiferroic perovskite PNMW was prepared by a solid-state reaction route using routine steps. Analytical-grade oxides: PbO, NiO, MnO2 and WO3, were weighed according to their molar ratios to get the desired formulation and mixed manually for 2 h in an agate mortar and pestle. Then, ?nal formulation is mixed again in ethanol atmosphere to get homogeneous powder of the sample. Then, mixed powder was ?red ( calcined) at different temperatures several times to optimize calcinations temperature, and hence powder was ?nally calcined at 1073 K for 4 h. It is to be mentioned that calcinations process was repeated to ascertain whether desired compound has been formed. For this process, preliminary analysis of X-ray diffraction (XRD) data and pattern collected on the powder sample using powder diffractometer (model D8 Advance of M/s Bruker Co) with k =
2：5405 A? between 20(cid:
3) and 100(cid:3) was carried out. Once the formation of PNMW was con?rmed, pellets of 10 mm diameter and around 1–2 mm thickness were prepared and sintered at optimized temperature 1133 K for 12 h followed by slow cooling to room temperature for 24 h. One of the samples was chosen for surface morphological study by scanning electron microscope (SEM, model JEOL-JSM-6400) at 20 kV. Another pellet was painted with a high-conducting silver paint on its both the faces/sides and annealed at 423 K for 1 h to ensure the complete removal of the moisture, if any. Also, the continuity of electroding on the surface was checked before the electrical characterization. Some electrical properties of the sample such as dielectric constant, dielectric loss, AC conductivity were obtained by means of LCR or impedance meter (phase sensitive meter, PSM), scanned between 102 and 106 Hz at different temperatures (298–573 K). The magnetoelectric coupling coef?cient was obtained by the magnetoelectric (ME) loop using a magnetoelectric instrument (M/s Marine India with an ampli?er SR 830). The source of DC ?eld was produced using a Helmholtz coil of diameter = 5 cm and number of turns = 200 to induce the DC magnetic field.
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