Magnetic, dielectric and magneto-dielectric properties of Aurivillius phase Bi_(4.25)Nd_(0.75)FeTi_2(NbCo)_(0.5)O_(15) ceramics

摘要

The structural, magnetic, dielectric and magneto-dielectric properties of Aurivillius phase Bi4.25Nd0.75FeTi2(NbCo)(0.5)O-15 (BNFTNCO) ceramics were investigated. X-ray diffraction and Raman results suggest that Nd ions can be effectively incorporated into Bi sites. A typical four-layered Aurivillius structure is confirmed by high resolution transmission electron microscope. The double remanent magnetization 2M(r) at 300 K is determined to be 0.88 emu/g, which is one order of magnitude larger than that of Bi5Fe0.5Co0.5Ti3O15 ceramic. The sample undergoes the ferromagnetic and ferroelectric transition at 642 K and 1094 K, respectively. The ferromagnetic Curie temperature is about 200 K higher than that of Bi4.2Nd0.8Fe0.5Co0.5Ti3O15 ceramic. The dielectric relaxation around 300 K with activation energy of 0.435 eV is associate with the hopping process of oxygen vacancies, while the high-temperature dielectric relaxation with a rather large activation energy of E-a= 2.43 eV may be related to the viscous motion of domain walls. More importantly, the intrinsic magneto-electric coupling effect with the magneto-dielectric constant of - 0.57% can be achieved at 300 K and 1 kHz. In addition, the optical band gap E-g of BNFTNCO is 2.50 eV.