NBT BT Ceramics Research Articles

Investigation of electrocaloric effect and scaling behavior with correlation of structural, electrical, and impedance properties in Sn-substituted NBT–BT ceramics near MPB

As is well known, relaxor dielectrics are characterized by high energy storage efficiency (η), while high recoverable energy storage density (Wrec) can be achieved by anti-ferroelectric ceramics. Herein, our approach is to find relaxor- anti-ferroelectric coexistence phases of (Bi0.5Na0.5)TiO3- BaTiO3 ceramics for achieving high performance in energy storage and energy harvesting as well. Therefore, [(0.9-x) ( Bi0.5Na0.5)TiO3-xSrTiO3-0.1BaTiO3] (abbreviation (0.9-x) NBT-0.1BT-xST) (0.0 ≤ x ≤ 0.4) were synthesized via the solid-state reaction route in air. The tolerance factor (τ) increased from 0.9901 to 0.9998 when ST-content increased from 0.0 to 0.4, indicating an increase in crystal lattice symmetry. The FT-IR de-convolution vibration modes shown in the TiO6 octahedra exhibit two peaks at ∼550 and 650 cm−1, which indicate present coexistence phases of the crystal structure. Ferroelectric to relaxor phase crossover has been detected by the addition of ST with the present anti-ferroelectric phase in particular dopant ST = 0.2. The increasing into the diffused phase transition (γ) is signified by enhancement of the relaxor degree of NBT-BT at high content of ST. The rapidly suppressed remnant polarization (Pr) at high content of ST is due to substitute iso-valence (Sr2+) by tri-valence (Bi3+) and mono-valence (Na1+). Ultrahigh Wrec = 1.13 J/ cm3 with excellent η = 92.62% were obtained at ST = 0.3 at low electric field (E = 110 kV cm−1). A remarkable response of the strain with a high converse piezoelectric coefficient ( d33* = 390.47 pm V−1) at ST = 0.2 was obtained due to decreasing the non-revisable 180° domain switching. Based on the obtained results, the addition of ST to NBT-BT ceramics can provide a head start in the implementation of ceramic capacitors for potential effective into energy harvesting and energy storage applications.

Energy storage, electrocaloric and optical property studies in Ho-modified NBT – BT lead-free ferroelectric ceramics

We report the effect of partial substitution of Dy3+ rare earth ion in NBT-BT lead free ceramics on its structural, microstructural, ferroelectric and dielectric phase transitions. The Rietveld refined X-ray diffraction analysis revealed a coexistence of dual phase with major monoclinic (Cc) along with minor tetragonal (P4mm) in all Dy-NBT-BT ceramics. The T-dependent dielectric broad band spectroscopic study revealed that Dy-substituted NBT-BT ceramics exhibits two diffuse dielectric anomalies renowned as Ferro (FE) to anti Ferro (AFE) i.e., depolarization phase transition ( $$T_{d}$$ ) and Antiferro (AFE) to paraelectric (PE) i.e., curie phase transition ( $$T_{C}$$ ), below 150 °C and well above 300 °C temperature regions respectively. The complex frequency dependent dielectric and modulus spectroscopy analysis supports the Non-Debye type dielectric relaxation process was dominated for all the measured ceramics. T-dependent AC-conductivity study revealed, thermally activated charge carries and single ionized oxygen vacancies are found to contribute conduction process at different temperature regions. Room temperature polarization hysteresis (P–E) loops analysis exposed a slim asymmetric shape with Dy substitution increasing that indicates conversion of hard to soft ferroelectric character. Remnant polarisation ( $$P_{r}$$ ) and coercive field ( $$E_{c}$$ ) decreases with dopant concentration shows the tetragonality dominance with Dy substitution. Furthermore, an optimum recoverable energy density 1.477 J/cm3 was obtained in NBT-BT at Dy = 0.03 compositions that designate the materials could be useful for future high energy storage density applications.

Low electric field induced high energy storage capability of the free-lead relaxor ferroelectric 0.94Bi0.5Na0.5TiO3-0.06BaTiO3-based ceramics

(Na0.5Bi0.5)0.94Ba0.06TiO3 + 0.3 wt.% Sm2O3 (named NBT-BT) lead-free piezoelectric ceramics were prepared by normal sintering. The effect of atmosphere sintering on NBT-BT ceramics was investigated through X-ray diffraction, dielectric, ferroelectric and piezoelectric characterizations. Real (Z′) and imaginary (Z″) parts of the complex impedance of the materials were also investigated. Dielectric studies exhibit a diffuse transition phase and are characterized by a temperature and frequency dispersion of permittivity, and this relaxation has been modeled using the modified Curie–Weiss law. The variation of the imaginary part (Z″) of impedance with frequency at various temperatures shows that the Z″ values reach a maxima peak (Z″max). The appearance of single semicircle in the Nyquist plots (Z″ vs Z′) pattern at high temperatures suggests that the electrical process occurring in the material has a relaxation process possibly due to the contribution of bulk material only. It shows that the compound exhibit negative temperature coefficient of resistance (NTCR) type behavior usually found in semiconductors. The bulk resistance of the material decreases with rising temperatures similar to a semiconductor, and the Nyquist plot showed the negative temperature coefficient of resistance (NTCR) character of materials. Also, the frequency-dependent AC conductivity at different temperatures indicated that the conduction process is thermally activated process. The plots of the relaxation times τZ″ and τM″ as a function of temperature follow the Arrhenius law, where a single slope is observed with activation energy values come to near 1.70.

The development of ferroelectric (FE) ceramics with high recoverable energy-storage density (Wrec) critically affects the miniaturization and integration of advanced pulse-power capacitors. However, most lead-free FE materials have the shortcomings of large remanent polarization and low dielectric breakdown strength. In this work, a strategy of composition control was implemented to improve the Wrec of lead-free ceramics. The effects of Li and Nb ion incorporation on the structure, dielectric, and ferroelectric properties of the highly insulating (Na0.5Bi0.5)TiO3–BaTiO3 (NBT–BT) ceramic was investigated. X-ray diffraction analysis of the samples revealed that the pure phase was isostructural to (Na0.5Bi0.5)TiO3. Dielectric measurements exhibited two pronounced anomalies which shift a certain angle within the depolarization-temperature range. The effects of LiNbO3 content on the breakdown characteristics and discharge energy storage of NBT–BT ceramics were investigated. An enhanced discharged energy density of 1.05 J/cm3, calculated from a hysteresis loop, was observed at x = 4 mol%. The improved structure also resulted in an increase of up to 61% in breakdown strength.

Improved depolarization temperature via the ordered alignment of defect dipoles in (Na0.5Bi0.5)TiO3-BaTiO3 ceramics

MgO doped NBT-BT ceramics were prepared by the conventional electroceramic processing. The effects of MgO on the phase, microstructures and electrical properties of NBT-BT ceramics were systematically investigated. When doping content is more than 1%, a second phase appeared, which has great effect on dielectric, ferroelectric, and piezoelectric properties, such as the TF-R peak weakened, moved to the higher temperature, and eventually disappeared. When the doping content is above 1.5%, the ceramic samples show a strong relaxation. The detailed analysis and discussion can be found within this study.

Enhanced electrical properties in lead-free NBT–BT ceramics by series ST substitution

Synthesis, structural, morphological and electrical properties of NBT–BT ceramics for piezoelectric applications

Dielectric, optical, piezoelectric and ferroelectric studies of NBT–BT ceramics near MPB

Reduction of anti-ferroelectric temperature region in NBT-BT ceramics using 100 MeV O7+ ion irradiation

Effect of SHI irradiation on NBT–BT ceramics: Transformation of relaxor ferroelectric to ferroelectric nature

Synthesis, dielectric and relaxation behavior of lead free NBT–BT ceramics

In this paper, we present impedance spectroscopy of Sodium Bismuth Titanate-based materials belonging to (1-x) Na 1/2 Bi 1/2 TiO 3-x BaTiO 3(x = 0.04) (NBT–BT) system. NBT–BT ceramics are prepared by high temperature solid-state reaction method. X-ray diffraction technique showed single-phase polycrystalline sample with an ABO3 perovskite structure. Dielectric behavior and the impedance relaxation were investigated in a wide range of temperature (room temperature (RT) –500°C) and frequency (1 kHz–1 MHz). A broad dielectric constant peak was observed over a wide temperature range around the phase transition temperature. The complex impedance plot exhibited one impedance semicircle identified over the frequency range of 1 kHz–1 MHz, which is explained by the grain effect of the bulk. The centers of the impedance semicircles lie below the real axis, which indicates that the impedance response is a Cole–Cole type relaxation.

Effect of different templates on microstructure of textured Na 0.5Bi 0.5TiO 3–BaTiO 3 ceramics with RTGG method