Unusual Dielectric Relaxation in Lightly Doped n-Type Rhombohedral BaTi_0.85Zr_0.15O₃:Ta Ferroelectric Ceramics

Abstract

The dielectric properties of tantalum doped BaTi 0.85 Zr 0.15 O 3 were investigated. The conventional solid state reaction method was used to make the ceramic samples. The composition was close to the pinch point of the three structure phase transitions in BaTiO 3 . Powder X-ray diffraction result indicated that the samples were in very slightly distorted rhombohedral structure at room temperature, and the dielectric measurement showed only cubic-to-rhombohedral phase transition occurred. Instead of a sharp peak characteristic of a ferroelectric (FE) transition, the large dielectric response was similar to those in nonferroelectric perovskites CaCu 3 Ti 4 O 12 , AFe 1/2 B 1/2 O 3 (A=Ba, Sr, Ca; B=Nb, Ta, Sb) and IBLC (Internal Barrier Layer Capacitance) BaTiO 3 based FE ceramics. However, unlike its FE analogue, the conventional BaTiO 3 based IBLC ceramics, our samples showed weaker temperature dependence of relative permittivity which spans over a wide temperature range. A Maxwell-Wagner type relaxation in the FE state was observed. Moreover, another relaxation mode appears from the vicinity of FE phase transition temperature T C , and extends over a narrow temperature range, with unusual slowing down of relaxation rate as temperature rises, which is contrary to what is commonly observed. We associate these unusual phenomena with the very slightly distorted rhombohedral structure of our samples and the presence of the grain boundary barrier layer where oxygen vacancies distribute non-homogeneously.

Dielectric behavior and phase transition in perovskite oxide Pb(Fe1/2Nb1/2)1−xTixO3 single crystal

“…1, 3 On basis of the data in Fig. 3, we can plot the curve of the logarithm of the relaxation time versus 1 / T, as shown in Fig.…”

“…A step size of 0.05°with a step time of 1 s was used for the 2 range of 10°-70°. As-grown crystals were oriented along the ͗001͘ cub direction on basis of the XRD results and were cut into the dimensions of 5 ϫ 5 ϫ 1 mm 3 . The asprepared samples were sputtered with gold to create two electrodes on either side of the sample.…”

“…So far, many materials with high dielectric constant have been reported; [1][2][3] however their dielectric constant shows strong temperature and frequency dependence, which is undesirable for the application in microelectronics. 4 Recently, complex perovskite oxide CaCu 3 Ti 4 O 12 ͑CCTO͒ crystals have attracted much attention 1,2 because of their colossal dielectric constant ͑ϳ10 5 ͒ around room temperature and a flat temperature dependence of the dielectric constant over a broad temperature range.…”

“…Such temperature independent behavior can occur either at low or high temperatures depending on the physical mechanism and the characteristic thermal activation energy. 3 Jha et al 4 reported that the presence of a partially filled d-band, as present in metallic copper, gives rise to conducting ͑often superconducting͒ properties in copper-based materials, which may also apply to the Cu containing perovskite oxide. To develop dielectric materials with even better properties, we have chosen to replace the copper in the complex perovskite oxide with iron atoms.…”

Hydrothermal synthesis and properties of NiFe2O4@BaTiO3composites with well-matched interface

“…Nevertheless, a well-matched interface between ferrite and BaTiO 3 was produced with a wet chemical method by carefully controlling the experimental conditions [27,36,37]. Oxygen vacancies are the most common defects in perovskites and spinels, and are formed during sintering at high temperatures and low partial oxygen pressures [38]. Such defects appearing at the interface will act as charge traps, resulting in a high dielectric loss.…”