Kumara Raja Kandula

Multifunctional Nd3+ substituted Na0.5Bi0.5TiO3 as lead-free ceramics with enhanced luminescence, ferroelectric and energy harvesting properties

Herein, we present comprehensive investigations of the optical and electrical properties of Nd3+ substitution in sodium bismuth titanate ceramics (NBNT) with varying Nd3+ concentration. The room temperature photoluminescence (PL) emission for both unpoled and poled samples is observed to be a maximum for an Nd3+ substitution of 1 mol%. Upon poling, the PL intensity is observed to be quenched, consistent with the obtained XRD data, indicating an electric-field induced structural ordering towards higher symmetry, confirmed with the help of structural refinement. The evaluated ferroelectric to relaxor and antiferroelectric relaxor T(F–R) was observed clearly from the poled dielectric–loss curve for the 1 mol% of Nd3+ substitution. Furthermore, the optimized NBNT exhibited a lower Ec and a higher off-resonance figure of merit (FOMoff) for energy harvesting by 12% and 30%, respectively, in comparison with un-doped NBT.

Enhancement in electrical and optical properties by substitution of lanthanides (Nd3+ and Eu3+) in lead free Na0.5Bi0.5 TiO3 ceramics

ABSTRACT The eco-friendly Na0.5Bi0.5TiO3 (NBT) and its derivatives have been synthesized by conventional solid state route. According to Judd-Ofelt theory, the higher symmetry phase suppresses the electrical and optical properties. Here, the ferroelectric and photoluminescence (PL) properties are influenced by the crystal structure symmetry. In the present work, these properties are optimized with minimal substitution of Nd and Eu at Bi-site in the NBT for introducing PL as an extra functionality without compromising ferroelectric properties. The evolution of photoluminescence in the visible and infrared region has been observed which may be useful in the field of piezochromic based devices.

Effect of La3+-donor substitution on structural, micro structural, dielectric and ferroelectric characteristics of BLNT-BZT solid solutions

ABSTRACT Lanthanum (La)-modified 0.93(Bi0.5−xLaxNa0.5TiO3)–0.07(BaTi0.96Zr0.04O3) (Abbreviated as BLNT-BZT) ceramics were synthesized (close to MPB) by using conventional solid state route. The structural phase purity of ceramics was confirmed by using room temperature (RT) X-ray diffraction. The structural phases coexistence was analyzed with different duel phase model and bring out the amount of phase contribution quantitatively with the help of Rietveld refinement technique. The X-rays diffraction studies revealed that coexisting of minor tetragonal (P4mm) phase evolution along with major monoclinic structural (Cc) phase. Moreover, the above affirmation was clarified from Raman studies, observed that TiO6 reflection at 500–600 cm−1 splitting occurs resides the presence of MPB of ceramics. With the substitution of La in BNT–BZT induces the gradual change in the average grain size and non-uniform distribution was observed from the surface morphology. The dielectric anomalies of these BLNT-BZT ceramics show broad dielectric anomaly near the maximum dielectric constant, which reflects the diffuse phase transition behavior. The RT P-E loops were observed in slim and slanted shape, replicates the enhanced properties due to the phase additive behavior near the MPB.

A lead free 0.96(Na0.5Bi0.49Nd0.01TiO3) -0.04BaTiO3 piezoceramic for possible optoelectronic device applications

Recent studies on (0.96)Na0.5Bi0.5TiO3–(0.04)BaTiO3 (NBT-4BT)solid solution reveal the existence of the structural distortion of lower symmetric Cc phase rather than the R3c phase through high resolution X-ray diffraction and neutron diffraction. The Nd-modified NBT-4BT can be thought of a possible candidate for switchable optical properties and has been chosen for present studies. The structural distortion in this solid solution is found to be mixture of two structural phases. The coexistence of Cc along with minor phase reflections of P4mm was confirmed through structural refinement The systematic study of structural, electrical and optical properties on this solid solution has been performed.

Improved ferroelectric and photoluminescence properties in Pr3+ substituted Na0.5Bi0.5TiO3 synthesized using hydrothermal route

Nanocrystalline Pr3+ substituted NBT was synthesized using hydrothermal technique. Pr3+ modifies the ferroelectric NBT optically active and enhances the electrical properties with small structural changes. Aiming to the development of the bottom up optoelectronic devices this optimized nanoscale Na0.5Bi0.5-xPrxTiO3(x = 0.005) compound is synthesized hydrothermally. X-ray diffraction pattern shows that the system is stabilized in the Rhombohedral (space groupR3c) phase indicating the local strain inhomogeneity. PE loop shows that there is a decrement in the Ec value compared with compounds synthesized using conventional methods. The strong red emission assigned to prominent transition of the Pr3+ ions at 610nm was observed along with weak blue-green emission, indicating the potential use of the system. Energy transfer from host system to Pr3+ ions is responsible for red emission while blue green emission is due to quenching of 3P0 induced by intervalence charge transfer state.

Enhanced energy storage density in lead free (Na0.5Bi0.48Eu0.02)Ti1-xNbxO3(x=0.00, 0.01 & 0.02) ceramics

Eco friendly (Na0.5Bi0.48Eu0.02) Ti1-xNbxO3 ceramics were synthesized with help of conventional solid state reaction by using high energy ball milling. The room temperature XRD of Nb5+ substituted NBET ceramics were stabilized in single phase pervoskite structure without any secondary phase. Polarization study reflects long range ferroelectric order for pure NBET ceramics and coercive field enhance with the substitution of Nb5+ ion at Ti site. Further, the substitution of Nb5+ ≥ 0.02 composition induced relaxor future. The energy density calculation shows the maximum energy storage density of 1.02 J/cm3 for x=0.02 ceramics. These results confirms a small fraction of Nb5+ doped NBET ceramics should be good candidates for energy storage applications.Eco friendly (Na0.5Bi0.48Eu0.02) Ti1-xNbxO3 ceramics were synthesized with help of conventional solid state reaction by using high energy ball milling. The room temperature XRD of Nb5+ substituted NBET ceramics were stabilized in single phase pervoskite structure without any secondary phase. Polarization study reflects long range ferroelectric order for pure NBET ceramics and coercive field enhance with the substitution of Nb5+ ion at Ti site. Further, the substitution of Nb5+ ≥ 0.02 composition induced relaxor future. The energy density calculation shows the maximum energy storage density of 1.02 J/cm3 for x=0.02 ceramics. These results confirms a small fraction of Nb5+ doped NBET ceramics should be good candidates for energy storage applications.

Evidence of suppressed oxygen vacancies in Sm and Sc co-substituted BiFeO3

BiFeO 3 (BFO) is well known room temperature multiferroic among all perovskite kind multiferroics. It shows very high ferroelectric Curie temperature T C = 1103 K and Neel temperature T N = 643 K [1]. The coupling between spin and charge in it would have an additional degree of freedom of changing magnetization by electric field and vice versa. However, the presence of oxygen vacancies and Fe 2+ /Fe 3+ ions lead to the leakage current which limits the potential of BFO in device applications [2]. It has been found that substitution of elements at A - site and/or B - site is quite effective to tackle these issues and to improve the physical properties. It is reported that A - site substitution by rare earth is quite effective in tuning the properties of BFO [2]. In a ddition to this, substitution of Sc at B - site reduces the leakage current and improves the insulating character of BFO [3]. It can be anticipated that co - substitution of Sm at A - site and Sc at B - site would improve the insulating character by reducing the l eakage currents and enhances the physical properties of BFO. In this work, polycrystalline BFO and Bi 0.85 Sm 0.15 Fe 0.90 Sc 0.10 O 3 (BSFSO) compounds were synthesized and their structural, dielectric and electrical properties were analyzed.

Improved magnetization and reduced leakage current in Sm and Sc co-substituted BiFeO3

BiFeO3 (BFO) and Bi0.85Sm0.15Fe0.90Sc0.10O3 (BSFSO) ceramics were synthesized by conventional solid state route. X-ray diffraction measurements revealed that an orthorhombic Pnma structure evolved with a phase fraction of 84% in the rhombohedral R3c structure of BFO upon the substitution of Sm and Sc. The changes in the intensity and the frequency of Raman modes also corroborated the structural transformation in the BSFSO compound. A decrease in grain size, reduction in porosity, and improved density were observed in the BSFSO compound. An enhanced remanent magnetization of 0.2 emu/g and coercive field of 6.2 kOe were observed, which were attributed to the structural change as well as the destruction of the spin structure with the substitution. Impedance and leakage current measurements revealed that the insulating character of BFO was improved with the substitution of Sm and Sc in BFO and was explained based on the bond enthalpy concept. The enhanced magnetic properties along with the improved insulating character of BSFSO compound will be suitable for device applications.BiFeO3 (BFO) and Bi0.85Sm0.15Fe0.90Sc0.10O3 (BSFSO) ceramics were synthesized by conventional solid state route. X-ray diffraction measurements revealed that an orthorhombic Pnma structure evolved with a phase fraction of 84% in the rhombohedral R3c structure of BFO upon the substitution of Sm and Sc. The changes in the intensity and the frequency of Raman modes also corroborated the structural transformation in the BSFSO compound. A decrease in grain size, reduction in porosity, and improved density were observed in the BSFSO compound. An enhanced remanent magnetization of 0.2 emu/g and coercive field of 6.2 kOe were observed, which were attributed to the structural change as well as the destruction of the spin structure with the substitution. Impedance and leakage current measurements revealed that the insulating character of BFO was improved with the substitution of Sm and Sc in BFO and was explained based on the bond enthalpy concept. The enhanced magnetic properties along with the improved insulating...