Properties Of Lead-free Na0 Research Articles

Role of B-site disorder in the properties of lead-free Na0.5Bi0.5(Mg1/3Nb2/3)O3 ceramic: A possible electrocaloric material with low leakage current

The electrocaloric (EC) effect in ferroelectric materials has been studied extensively to develop materials for solid-state cooling applications. The Na0.5Bi0.5TiO3-based ferroelectric material is selected for this particular application. The Ti4+ of the lead-free Na0.5Bi0.5TiO3 is completely replaced by (Mg1/3Nb2/3)4+ to enhance the dielectric breakdown strength and to observe the EC effect. The lead-free Na0.5Bi0.5(Mg1/3Nb2/3)O3 is synthesized via the columbite route with optimized processing conditions. The material shows a frequency-independent high ferroelectric–paraelectric transition temperature (460 °C) with a slim polarization vs electric field loop. The adiabatic temperature change (ΔT) of the compound is evaluated from the temperature-dependent polarization behavior, and calculated ΔT is ≈ 0.135 K at room temperature. The room-temperature EC strength and leakage current of the material are examined to check its suitability for solid-state refrigeration.

Effect of BaSnO3 on structural and electrical properties of lead free Na0.5Bi0.5TiO3 ceramic solid solution

A series of novel lead-free (1-x)(Na0.5Bi0.5)TiO3–xBaSnO3, (x = 0.00, 0.05, 0.10) ceramics were fabricated by solid-state air sintering route and their dielectric and microstructural properties were studied. Various experimental methods to characterize the fabricated ceramics such as PXRD, Raman spectra, SEM-EDS, UV-visible and dielectric studies. All the ceramics were crystallized by rhombohedral symmetry using PXRD and Rietveld profile refinement technique. The experimental atomic charge density distribution studies were performed and the bonding characteristics were analyzed. With increase of BSN content, the average grain size decreased and was characterized by scanning electron microscopy (SEM) technique. Energy dispersive x-ray (EDS) spectra indicate the presence elements and the diffusion of BSN into the rhombohedral phase of NBT matrix. The optical bandgap was determined by UV-Visible spectra and the values are found to be 3.05, 3.10 and 3.12 eV. The temperature dependence of dielectric constant (ε) provides evidence for dielectric anomalous behaviour in the higher doping of BSN concentration.

Properties of Na 0.5Bi0.5TiO3 and Na0.5Bi0.5 TiO3-based single crystals

Most studies of ferroelectric materials were focused on polycrystalline ceramics. However, it is difficult to improve their properties significantly (particularly piezoelectric one) due to grain/grain boundaries, compositional homogeneity, isotropic characteristics, and structural defects. It is commonly accepted that single crystals often have better piezoelectric behavior and less structural defects than ceramics. In this paper, we provide the processing technology and properties of lead-free Na0.5Bi0.5TiO3 and Na0.5Bi0.5TiO 3-based single crystals. #FERROELECTRICS #NBT_SINGLE_CRYSTALS #FLUX_METHOD #CZOCHRALSKI_METHOD #DIELECTRIC_PROPERTIES

Effect of SrTiO<sub>3</sub> Nano-Crystals on the Dielectric Properties of Na<sub>0.47</sub>K<sub>0.47</sub>Li<sub>0.06</sub>NbO<sub>3</sub> Ceramics by Seed-Induced Method

A solid-state reaction method is generally used to fabricate ceramics. This work studies the influence of heterogenous nano-crystallites on electrical properties of lead free Na0.47K0.47Li0.06NbO3 (NKLN) ceramics by adding SrTiO3 nano-crystals as the initial phase of reaction. The lead-free piezoelectric ceramics were synthesized by the seed-induced method. The SrTiO3 nano-crystals used as seeds were prepared by molten salt technique. The seed content was varied from 0 to 10.0 mol%. The investigation reports microstructure and electrical properties of ceramics. The XRD showed a mixed tetragonal and orthorhombic phase structure. Tc decreasing with increased SrTiO3nano-crystal concentration.

Structural, dielectric and ferroelectric properties of lead-free Na0.5Bi0.5TiO3 ceramics prepared by spark plasma sintering technique

Lead-free Na0.5Bi0.5TiO3 (NBT) fine-grained ceramics were prepared by spark plasma sintering method. Single phase ceramics with an ABO3 perovskite structure were confirmed by X-ray diffraction method. The grain morphology was analyzed by using a scanning electron micrograph. The crystal particles arranged compactly and the typical grain size was about ≈200 nm. The depolarization temperature T d, the rhombohedral–tetragonal phase transition temperature T R−T and the temperature T m of the maximum dielectric constant corresponding to tetragonal–cubic phase transition were determined to be 453 K, approximately 623 and 793 K, respectively, from the temperature dependence of dielectric properties. The P-E hysteresis loop at different temperatures indicated the existence of antiferroelectric state at the depolarization temperature T d, which explained the antiferroelectric phase above T d. The values of P s, P r and E c reduced slightly with increasing temperature in the range 303–453 K.

Enhanced electric field tunable magnetic properties of lead-free Na0.5Bi0.5TiO3–MnFe2O4 multiferroic composites

Strong magnetoelectric (ME) interaction was exhibited at both dc and microwave frequencies in a lead-free multiferroic particulate composites of Na0.5Bi0.5TiO3 (NBT) and MnFe2O4 (MFO) multiferroic, which were prepared by sol–gel route. The room temperature permeability measurements were carried out in the frequency range of 1 MHz–1 GHz. A systematic study of structural, magnetic and ME properties were undertaken. The room temperature ferromagnetic resonance (FMR) was studied. Strong ME coupling is demonstrated in 70NBT–30MFO composite by an electrostatically tunable FMR field shift up to 428 Oe (at E = 4 kV/cm), which increases to a large value of 640 Oe at E = 8 kV/cm. Furthermore, these lead-free multiferroic composites exhibiting electrostatically induced magnetic resonance field at microwave frequencies provide great opportunities for electric field tunable microwave devices.

Phase structure and electrical properties of lead free Na0·5Bi0·5TiO3–CaTiO3 ceramics

(1−x)Na0·5Bi0·5TiO3−xCaTiO3 ceramics with x = 0–0·2 were prepared by solid state sintering method. Structural and morphology studies carried out by X-ray diffraction and scanning electron microscopy indicate the change in crystal structure from rhombohedral to orthorhombic symmetry (R3C to Pnma). The morphotropic phase boundary of this system was found to lie around x = 0·08–0·14, where the orthorhombic and rhombohedral symmetries coexist. The orthorhombic phase is stabilised for x>0·14, indicating that the rhombohedral phase of Na0·5Bi0·5TiO3 is susceptible to orthorhombic distortion brought about by Ca substitution. Calcium substitution in Na0·5Bi0·5TiO3 caused an obvious decrease in peak temperature and a decrease in relative permittivity. The compositional variation of the fundamental dielectric behaviour is discussed in relation to the crystal chemistry of the system. The highest piezoelectric constant d33 of 85 pC N−1 is achieved for x = 0·1, with the coercive field of 18 kV cm−1 and the dielectric maximum temperature of 148°C.

Piezoelectric Properties of Lead-Free Na0.5K0.5NbO3 Ceramics Co-Doped with NiO and CuO

Lead-free Na0.5K0.5NbO3 + 0.5 mol% NiO+y mol% CuO (y = 0∼3) piezoelectric ceramics have been prepared by conventional solid state reaction technique. The crystal structure and microstructure were analyzed using X-ray diffraction and scanning electron microscopy, respectively. The results indicated that the co-doping of NiO and CuO was very effective in densification of ceramics. The KNN ceramics co-doped with 0.5 mol% NiO and 2 mol% CuO exhibited high mechanical quality factor of Qm = 1556 and electromechanical coupling coefficient of kp = 0.40. This material is promising for high frequency applications such as transformers and ultrasonic transducers.

Dielectric and Piezoelectric Properties of Lead Free Na0.5K0.5NbO3–BiScO3 Ceramics

A well-known Bi-containing perovskite ferroelectric, BiScO3 (BS), was successfully utilized to develop Na0.5K0.5NbO3 (NKN)-based lead-free piezoelectric ceramics, in which there is a morphotropic phase boundary (MPB) between ferroelectric orthorhombic and rhombohedral phases. The addition of a small amount of BS tends to promote the sinterability of NKN ceramics, and simultaneously, to retard the grain growth, and change the crystalline structures, resulting in a dense (1-x)NKN–xBS solid-solution ceramic upon conventional sintering. Enhanced piezoelectric and electromechanical properties appear near the MPB composition with x=0.02, the piezoelectric constant being 210 pC/N and the planar electromechanical coupling factor being 45%. This material also has a comparable Curie temperature (340 °C) to that of commercial Pb(Zr,Ti)O3 as well. All these results reveal that BS-substituted NKN ceramics may become promising candidates for lead-free piezoelectric materials.