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The present study is focused on the structural correlation of magneto-electric coupling that exists in polycrystalline TbMnO 3 . The X-ray diffraction patterns are collected at various conditions, which are (1) at 300 K without a magnetic field, (2) at 2 K without magnetic field and (3) at 2 K with 7 Tesla magnetic fields. The structural transition in TbMnO 3 has been observed at 2 K and some lattice modulation after applying the magnetic field at 2 K. The Rietveld refinement of TbMnO 3 confirms the orthorhombic phase with centrosymmetric space group Pnma at 300 K. We have observed that the inversion symmetry breaks at 2 K and the polycrystalline TbMnO 3 has been refined using a non-centrosymmetric orthorhombic space group which can be either Pn2 1 a or P2 1 ma. This structural transition confirms the presence of a ferroelectric phase at 2 K. After the application of 7 Tesla magnetic field, the signature of an incommensurate phase has been observed in polycrystalline TbMnO 3 at 2 K. The DC magnetization behaviour with temperature M(T) and field M(H) reveals the antiferromagnetic behaviour of polycrystalline TbMnO3 below 42 K. We have also measured magneto-dielectric property of polycrystalline TbMnO 3 at the low temperature, which confirms the strong magneto-electric coupling in polycrystalline TbMnO 3 below the transition temperature.

Doping of nonmagnetic impurities in technologically important ZnO has opened a new window for achieving room temperature ferromagnetism, p-type carrier conduction, and enhancement of ferroelectric properties. Here, we report on the confined optical phonon and bandgap engineering in highly oriented Li implanted ZnO thin films. Using resonance Raman scattering condition, the confined longitudinal optical phonon lineshapes in uniaxial hexagonal wurtzite crystal are analyzed in detail using the phonon confinement model. We have demonstrated that phonon confinement model can yield a meaningful result for the interpretation of resonance Raman lineshapes if one considers the contribution of both the E1 (LO) and A1 (LO) modes, particularly while dealing with oriented ZnO thin films. Furthermore, with the increase in Li dose, the bandgap of ZnO is found to show a blue shift, and such blue shift in bandgap is explained using first principles calculation.

While controlling atomic positions in mixed phases in composite materials is difficult, electrical coupling of the different phase components is attractive. This research studied effects of misfit layered structure added into perovskite structure in order to investigate microstructure and ferroelectric properties of Pb(Zr0.52Ti0.48)O3 (PZT) and Ca3Co4O9 (CCO) composites. The composite materials of PZT-CCO showed a small proportion of monoclinic phase that was found to strongly influence the PZT phase. The microstructure exhibited heterogeneity of PZT and CCO. FE-SEM showed that grain size decreased with increasing CCO content. Co atoms migrated towards center of curved grain boundaries. The charge carriers of CCO affected domain wall movements in the PZT under high temperature. Dielectric maximum temperature alternated due to the affected charge mechanism in the CCO. Polarization-electric field loops revealed that saturated polarization and domain switching decreased with increasing CCO content and temperatures. Capacitive and resistive behaviors as well as remanent polarization were increased with increasing CCO content at high temperatures. Electric field was accounted for current density causing leakage current. It is expected that the PZT-CCO composite materials developed will have electrical performance suitable for some electronic devices.

Ferrite-ferroelectric composites having general formula (1-x)Na0.5Bi0.5TiO3-(x)Ni0.25Mg0.5Zn0.25Fe2O4 were developed by conventional solid state reaction method. The structural, dielectric and magnetic properties were studied for all the prepared samples. The crystalline phases of samples were verified by XRD. Rietveld refinement pattern confirms the coexistence of cubic ferrite phase as well as rhombohedral ferroelectric phase in the composites which make them promising candidate for versatile applications. The tangent loss (tanδ) and dielectric constant (eʹ) both shows dispersion at lower frequencies. From the Nyquist plot of impedance, the effect of grain and grain boundaries on the electrical properties was examined. From Arrhenius plot, it was found that dc conductivity and activation energy of all the compositions increases with increase in temperature. Magnetic parameters were found to be increased as the ferrite phase is increased which provides information regarding the intercoupling between the ferroelectric and magnetostrictive ferrite phases. These ME composites are found to be useful in memory devices.

In this study, the conventional and inverse barocaloric effects (BCE) in ferroelectric NH4HSO4 are reported. Maximum extensive and intensive BCE near order–disorder phase transition can be achieved at low pressure p ≤ 0.1 GPa. Large thermal expansion of the crystal lattice plays a very important role in the developing conventional BCE and conversation between BCE of different sign in the narrow temperature range.

Bi(Li0.5Nb0.5)O3 (BLN) was adopted to tailor the Curie temperature (TC) and the resulting ferroelectric and electrostrictive properties of solid solutions of the morphotropic phase boundary relaxor ferroelectric 0.67 Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (0.67PMN-0.33 PT). The ceramic samples were synthesized by a solid reaction method, and the BLN content was set to 2.5 at.%, 5 at.%, 7.5 at.%, and 10 at.%. X-ray diffraction results suggested that BLN cannot enter the 0.67PMN-0.33 PT crystal lattice completely, resulting in the formation of a second phase (Pb2Ti2O6 with pyrochlore structure) in all the samples. With increasing BLN content, a decrease in TC and a ferroelectric-to-relaxor transition were revealed by the dielectric and ferroelectric properties. High electric-field-induced strains of 0.167%–0.228% with low hysteresis (

Dielectric and magnetocaloric measurements are carried out for the chromite TmCrO3. This oxide was reported to be multiferroic below the Neel temperature (TN) of ∼125 K, likely due to a structural transformation. The dielectric response shows large dielectric constants below 300 K. However, from the analyses of loss tangent, AC conductivity and dielectric modulus, this behavior is rooted in hopping of charge carriers rather than electric dipoles, as proposed for some other chromites. No dielectric anomaly is found at TN. The magnetocaloric effect shows that the magnetic transitions at TN as well as the spin reorientation temperature are of a second order. This result strongly suggests the absence of magnetostructural transition at TN in accord with no observation of ferroelectric transition at this temperature.

Magnetocaloric effects, because of their large entropy change, have been demonstrated to potentially revolutionize the solid-state cooling devices with high energy efficiency and environmental friendliness. However, the requirement of applying large magnetic fields obstructs the minimization of cooling devices. Here, we investigated electric-field-control magnetocaloric effects in magnetoelectric heterostructures by combining thermodynamic modelling and first-principle calculations. Based on strain-mediated mechanism, it is demonstrated that the interface strain of ferroelectric film under the electric field can tune the magnetic transition temperature from ferromagnetic to antiferromagnetic phases with 5 K shift under a small electric field of 0.1 MV/m and a giant entropy change of 14.9 J/(kg·K). In addition, we propose a potential multicaloric device including magnetocaloric and elastocaloric effects with high cooling efficiency based on magnetic-elastic-electric coupling phase transformations. The present study therefore contributes to the understanding of electric-field-control magnetocaloric cooling and provides guidance for experiments to design high efficiency and low-power consumption multicaloric cooling devices using magnetoelectric heterostructures.

In this work, the piezoelectric ceramics Pb0.95Ba0.01Sr0.04(Zr0.53Ti0.47)O3-1wt.%LiBiO2-0.06 wt.%CuO-xwt.%MnCO3 (PBSZT-LBCu-xwt.%MnCO3) were prepared by the conventional solid-state sintering method. The effect of MnCO3 on addition phase structure, microstructure, ferroelectric performances, piezoelectric and dielectric properties were systematically studied. It was found that the addition of MnCO3 can highly increase the mechanical quality factor (Qm) from a small value (

The microstructure, ferroelectric, electric-field breakdown strength, and energy-storage properties of relaxor Pb0.9La0.1(Zr0.52Ti0.48)O3 (PLZT) thin films grown on flexible Ti foils using pulsed laser deposition were systematically investigated. Low temperature deposited PLZT thin films showed very slim polarization hysteresis loops with a high difference between maximum and remanent polarizations and low remanent polarization through modulating the film structure with a small columnar-grain size. An ultrahigh recoverable energy density (Ureco) of 40.9 J/cm3, excellent energy efficiency (η) of 80.2% and large breakdown strength (EBD) of 3000 kV/cm were achieved in a PLZT film deposited at the low temperature of 480 °C. More importantly, this film shows excellent charge-discharge cycling endurance with a small variation of both Ureco and η values (less than 3%) after 1010 cycles and good thermal stability under a wide operating temperature range from room temperature to 200 °C. These results indicate that the relaxor PLZT films deposited on thin Ti foils, even at low temperature, are a promising strategy to enhance energy-storage performance for pulse-power energy-storage systems with broad temperature range applications, especially in applications where the device weight is critical (lightweight) due to the thin and low density of Ti foils.

In view of the vital role of temperature in actural applications of materials, a detailed investigation was conducted for Ho3+/Yb3+-modified Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PSN-PMN-PT) crystals focusing on their temperature dependence of upconversion luminescence and sensing abilities. The results indicated that the luminescence intensity of grown crystals weakened with elevating temperature, and the fastest decrease rate occurred in green emission. The absolute and relative sensitivities calculated by S755/S767 (SA2 and SR2) were higher than that based on I665/I554 (SA1 and SR1) at low temperature, and the maximum of 0.0112 K-1 and 0.0373 K-1 were obtained at 93 K, comparable to that of some rare earth (RE) doped host materials reported. The study on chromaticity coordinate revealed the high colour purity of crystals, nearly up to 99%. Furthermore, the decay dynamics of crystals were investigated. The longest average decay time (157.44 μs ) of 554 nm emission was obtained at 293 K. These results manifest the promising applications of Ho3+/Yb3+-modified PSN-PMN-PT crystals as luminescent and optical thermometric materials at low and room temperature. It is also of significance for further investigation of photoelectric coupling performance of ferroelectric crystals.1

A series of Bi0.48(Na0.84K0.16)0.48Sr0.04(Ti1-xTax)O3 (abbreviated as NKS-100xTa) lead-free piezoelectric ceramics were fabricated using a traditional solid-state method. The structure and electrical properties of NKS-100xTa were investigated in detail. The composition for x = 0.01 presented an enhanced electric field induced bipolar strain of ∼0.53%, as well as the giant unipolar strain of ∼0.478% corresponding to Smax/Emax ∼682 p.m./V at 70 kV/cm. It is found that the ferroelectric-relaxor transition temperature (TF-R) shifted down to ambient temperature and the remnant polarization (Pr) decreased with the Ta doping. It destroyed the long-range ferroelectric ordering and increased the relaxor characteristic. Therefore, the origin of giant strain was ascribed to the transformation from the ferroelectric phase to relaxor phase under the applied electric field. In addition, the well fatigue properties within 104 cycles indicated that the prepared ceramics offered extendable availability for sensors and actuators.

The introduction of acceptor dopants into perovskites is a common method for designing hard piezoelectric ceramics by forming defect dipoles. It is interesting to find that the doping effect of a few amount of MnO2 in (Bi0.5Na0.5)TiO3–BaTiO3 lead-free ceramics significantly depends on the local symmetry. A conventional hardening effect corresponding to an obviously enhanced mechanical quality factor and a decreased piezoelectric coefficient can be generated in the tetragonal phase rich zone, rather than in the rhombohedral-rich zone, where a typically amphoteric characteristic can be observed unexpectedly. The result was well interpreted by means of the formation of a local random field as a result of the local symmetry-breaking effect of point defects after doping MnO2 in addition to a traditional internal bias field as a result of the pinning effect of defect dipoles. Compared with tetragonal-rich ones, the obviously enhanced random field in rhombohedral-rich compositions tends to induce a weakening ferroelectricity, as evidenced by composition dependent normal ferroelectric-relaxor ferroelectric phase transition. This work provides a new understanding of how charged defects affect the domain stability in the matrix with different symmetries through the competition between random electric fields and internal bias fields.

High temperature ferroelectricity (T c ∼435 °C, E c ∼6.15 kV/cm & P r ∼0.16 μC/cm 2 ) was observed in a novel 3D hierarchical dysprosium (Dy)-doped ZnO nanorods-nanosheets (NRs-NSs) architecture synthesized using wet chemical co-precipitation method. Such a conclusion was drawn on the experimental confirmation obtained from the temperature variation of real part of dielectric constant and the room temperature P–E hysteresis loop. Dy 3+ doping strongly modified the morphology of ZnO from nanotaper to hierarchical NRs-NSs architecture. Lattice strain ( e ), crystallite size (L), deformation stress (σ), and deformation energy density (u) of both pristine nanotapers and 3D hierarchical Dy-ZnO NRs-NSs architectures were evaluated using line broadening analysis followed by the Debye-Scherrer and Williamson-Hall methods. Temperature variation of real component of dielectric constant ( e ′) for Dy-doped ZnO NRs-NSs architecture attains a maxima ( e ′ m ∼34,500) at ferro-to para-electric transition temperature, T c ∼435 °C. Temperature dependent complex component of dielectric constant ( e ''), tangent dielectric loss (tan δ) and ac conductivity (σ) were found to increase with rise in temperature. The frequency dependent dispersion plots of dielectric properties of Dy-ZnO NPs showed a decrease in dielectric constant and tangent loss with increase in frequency whereas ac conductivity showed an opposite trend. The Dy-doped ZnO NRs-NSs architectures exhibit feeble ferroelectricity with a remnant polarization (P r ) of 0.16 μC/cm 2 and a coercive field (E c ) of 6.15 kV/cm at room temperature. Moreover, the novel Dy-doped nanorods-nanosheets architectures with high temperature ferroelectricity will pave the pathway towards designing futuristic material in the field of low-power and wide-temperature ferroelectric based memory devices.

C-axis preferentially and randomly oriented Bi4NdTi3FeO15 (BNTF) ceramics were prepared by molten salt synthesis and conventional solid-state reaction methods, respectively. The ceramics with different orientations all exhibit Aurivillius structure containing four perovskite layers and the Lotgering factor f of c-axis preferentially oriented BNTF prepared by molten salt synthesis was calculated to be 0.865. BNTF powders show two absorption edges due to the electron excitations not only from valence band (VB) to Ti 3d conduction band (CB) but also to Fe eg CB. The ferroelectric and photovoltaic properties of BNTF ceramic samples were investigated. The ferroelectric performance of randomly oriented ceramic sample is better than that of c-axis preferentially oriented one. Significant photovoltaic effect was observed in both ceramic samples. Compared with the ceramic with c-axis preferred orientation, the randomly oriented ceramic exhibits a larger photocurrent Jsc and a smaller photovoltage Voc, which was discussed from the grain alignment in the two ceramics and the anisotropy of the crystal structure. The present work provides a new way to control photovoltaic properties of lead-free Bi5Ti3FeO15 (BTF) based compounds and accelerates their application in ferroelectric photovoltaic (FEPV) and energy fields.

Epitaxial BiFeO 3 thin films with (100), (110) and (111) orientations were grown on the SrRuO 3 -buffered SrTiO 3 substrates by using an off-axis magnetron sputtering. Unlike the BiFeO 3 (110) and BiFeO 3 (111) thin films that exhibited a single rhombohedral phase structure, a dominant rhombohedral phase accompanying with a small amount of tetragonal phase was identified in the BiFeO 3 (100) thin film. In particular, the leakage currents and ferroelectric polarizations of sputtered BiFeO 3 thin films were focused on and these films showed utterly different current density-electric field ( J - E ) behaviors whether in the positive or negative electric field. Among the three films, the ferroelectric polarization of the BiFeO 3 (100) thin film presented a good frequency stability and had the maximum remnant polarization of P r ∼ 78 μC/cm 2 @ 10 kHz, which could be further demonstrated by pulsed polarizations of films. The distinct differences in electrical properties of orientation-engineered BiFeO 3 thin films in present case can be attributed to their different crystallographic orientations and microstructures.

Influence of Bi-non-stoichiometry is studied on the dielectric and ferroelectric properties of 0.72Bi0.5+xNa0.5TiO3-0.22SrTi0.875Nb0.1O3-0.06BaTiO3 (BNBSNT) lead-free relaxors. All compositions exhibit high symmetry phase structure with dynamic polar nano regions. An enhanced degree of disorder is revealed and more polarization can be induced in Bi deficiency, which is related to the difficulty in the formation of a neutral defect complex between cations and oxygen vacancies. The relaxation of the two anomalies on temperature dependent permittivity is greatly affected by Bi non-stoichiometry especially that around the first dielectric anomaly temperature that can be deconvoluted by phenomenological models. The materials display a remarkable stability of high e′ (∼3000) over a wide temperature range (>320 °C) with considerably low loss (≤0.003) in the ergodic relaxor state. Significant improvement on energy storage properties as well as electrostrictive strain (Wrec = 0.86 J/cm3, η = 83%; S = 0.235%, strain hysteresis of 7.34% at a low electric field of 80 kV/cm for bipolar P-E loops) is achieved due to chemical disorder and strong random field caused by Bi3+ deficiency.

Comprehensive investigations on the effect of mechanical and chemical processing techniques on structural, electrical and photocatalytic properties of single phase lead-free Na0.5Bi0.5TiO3 (NBT) and their correlations are presented here. NBT is synthesized using solid-state (NBT-SSR), sol-gel (NBT-SG), combustion (NBT-C) and hydrothermal (NBT-H) techniques. The structural analysis confirmed the rhombohedral (R3c) phase stabilization in the solid-state synthesized sample whereas a minor monoclinic (Cc) phase coexisted with R3c phase in chemically synthesized samples. The robust relaxor feature along with slanted ferroelectric hysteresis loop (for energy storage) was observed in hydrothermally synthesized NBT samples (NBT-H). The ferroelectric hysteresis loop gradually became slanted due to the multi-domain to the mono-domain transformation that eased the domain reversal and switching which was observed through lower coercive field (Ec) values. NBT ceramics synthesized using combustion technique (NBT-C) appeared to be the best target catalyst to probe the influence of ferroelectricity on the decolorization of Rhodamine B dye under simulated visible light.

It remains a challenge to enhance the multiferroic properties of perovskite materials. Herein, we demonstrate a facile sol-gel synthesis of BiFeO3 and Bi0.98Ho0.02Fe1-xCrxO3 (x = 0.01, 0.02, 0.03 and 0.04) nanoparticles with an average size range of 71–35 nm. The crystal phase and structure of as-synthesized powders are studied using Rietveld refinement, which reveal 100% perovskite phase with rhombohedral R3c structure. A saturated loop with small remnant magnetization (Mr) reflects weak ferromagnetism in all the samples. The dc magnetization along with Mossbauer spectroscopy confirms ferromagnetic nature of the compounds. Further, it is to be noted that the co-doping enhances the saturation magnetization to almost three times more than that of pure BiFeO3 and related mechanism was studied in details. Simultaneously, the ferroelectric polarization (Pm) was found to increase from 0.44 μC/cm2 (pure BiFeO3) to 2.08μC/cm2 (Cr doped Bi0.98Ho0.02FeO3). The co-doped samples show high resistivity which is confirmed by the decrease of loss tangent (tanδ) from 3.6 to 0.17 due to the reduction of oxygen vacancies. The band gap of as prepared samples was also found to increase at higher Cr concentration. To the best of our knowledge, for the first time, we have attempted to enhance the multiferroic properties of BiFeO3 using Cr and Ho as co-dopants.

Di-phase ferroelectric-ferrite composites with the same composition close to the percolation limit (0.66BaTiO3-0.33CoFe2O4) and with different phase arrangements (randomly mixed phases and tri-layer structures) have been consolidated by using spark plasma sintering and their properties were comparatively analyzed. The intrinsic effective dielectric constant has been estimated by using finite element method and a value almost ten times higher was predicted for the randomly mixed composite, as result of different field distributions inside the ferrite and ferroelectric phases. At room temperature, experimental permittivity contains an intrinsic behavior overlapped onto a very strong extrinsic component determined by the interfaces and by local charge inhomogeneity. The extrinsic dielectric behavior has been discussed in terms of thermally activated relaxation mechanisms developed in both types of investigated structures, as revealed by the temperature-dependence impedance spectroscopy. The magnetic properties are derived as “sum property” from the ferrimagnetic character of CoFe2O4 and show the lowest magnetization for the randomly mixed composites and a weak magnetic anisotropy when the magnetic field was applied in-plane or out-of-plane in the layered structure. Due to the different levels of interface doping specific to the different types of interfaces, the magnetic Curie temperature of the two composites ranges from 720 K in the randomly mixed structure to 746 K for the layered one. The ferroelectric P(E) loops and a modest ME coefficient of 14 mVOe−1cm−1 at 100 Hz were determined only for the layered structure, due to the high leakage and to the small grain size (below 200 nm) in the ferroelectric BaTiO3 component.

The cerium orthoferrite (CeFeO3) ceramics were synthesized successfully by solid-state method and the room-temperature multiferroic properties of CeFeO3 annealed under different atmospheres were investigated. A clear ferroelectric hysteresis loop with Pr = 0.8 μC/cm2 measured under 10 kV/cm is observed at room temperature in the CeFeO3 annealed under oxygen, implying the nature of ferroelectricity existing in the material which is ascribed to the crystal structure change and local lattice distortion closely related to the mixed valences of Ce and Fe ions, as revealed by X-ray diffraction, Raman spectra, and XPS analysis. Besides, Magnetic study reveals that CeFeO3 is a weak ferromagnetic material and the saturation magnetization increases with oxygen vacancies decreasing. The coexistence of the induced ferroelectricity and the improved ferromagnetism confirms that the better multiferroic property exists in CeFeO3 ceramics and the oxygen content (Ce valence) has a critical role in the ferroelectric property.

Multiferroic BiFeO3 and Bi1-xSmxFe0.95Nb0.05O3 ceramics are successfully fabricated by spark plasma sintering combined with sol-gel powders. The effects of Sm and Nb co-doping on the structural, dielectric, ferroelectric and magnetic properties of the samples are investigated. With the Sm-Nb co-doping, the crystal structure of as-prepared samples transforms from R3c to Pnma and the grain size, loss tangent and leakage current density are reduced. The leakage current density of the co-doped samples can be reduced by approximately three orders of magnitude compared with the undoped sample. The dielectric, ferroelectric and magnetic properties are apparently enhanced due to the Sm-Nb co-doping. The optimal values of remanent polarization (Pr) and magnetization (Mr) of the created Bi0.85Sm0.15Fe0.95Nb0.05O3 ceramic are approaching up to 5.853 μC/cm2 and 0.187 emu/g, respectively. This enhancement of the multiferroic properties could be attributed to the co-doping-induced structural distortion, grain size reduction, oxygen vacancy decrease, space-modulated spin structure collapse as well as increased magnetic ions.

Luminescent piezoelectric materials promise a stratagem for controlling the optical process by electric field, which would benefit for future optoelectronic devices. Here, Er3+ doped (Ba0.85Ca0.15) (Zr0.1Ti0.9)O3 (BCZT: Er3+) piezoelectric ceramics are prepared to demonstrate the proof of concept. In addition to excellent intrinsic piezoelectricity and ferroelectricity, BCZT: Er3+ ceramics exhibit simultaneously strong green upconversion emissions under excitation of 980 nm. Remarkable photoluminescence (PL) quenching phenomenon as well as significant changes on relative intensities of stark lines are observed under external poling electric field. Furthermore, field dependent piezoelectric constant d33 and photoluminescence quenching ratio show similar variation trend and finally saturate for E > 3.5 kV/mm, which provides a noncontact strategy to monitor the piezoelectric constant d33. The PL quenching triggered by electric field in BCZT: Er3+ ceramics is ascribed to the decreased asymmetry originating from field-induced structural transformation from a significant fraction of the tetragonal phase to rhombohedral phase. Our work would be helpful for expanding the scope of luminescent piezoelectric materials and promising future optoelectronic and optical devices with cross-coupled physical properties.

We investigated the characteristics of ferroelectric non-volatile random-access memory field effect transistors (MoS2-BFO NVRAM FETs) consisting of monolayer MoS2 channels, BiFeO3 (BFO) gate layers, and Pt and SrRuO3 bottom electrodes on glass substrates. As a result of the comparative experiments of the Pt and SrRuO3 bottom electrodes, it was confirmed that the BFO gate layer using the SrRuO3 bottom electrode showed a higher remanent polarization, faster switching time, and superior fatigue endurance than the BFO gate layer using the Pt bottom electrode. It is suggested that the good ferroelectric properties of the BFO gate dielectric layer on the SrRuO3 bottom electrode is resulting from its (001)-oriented growth. The MoS2 BFO NVRAM FET with a SrRuO3 bottom electrode exhibited a wider memory window than the Pt bottom electrode because the SrRuO3 bottom electrode had a higher remanent polarization of the BFO gate layer compared to the Pt bottom electrode.

Designing ferroelectrics with excellent electrical performance and high-temperature electrical resistivity (ρ) without severely sacrificing their high Curie temperature (TC) is a major issue in the development of Bismuth Layer-Structured Ferroelectrics (BLSFs). In this regard, a novel solid solution of CaBi2Ta2O9 and Na0.5Bi2.5Ta2O9 was synthesized by conventional electroceramic procedures in this study and was found to possess enhanced piezoelectric and ferroelectric properties together with a high Curie temperature (TC ∼ 925 °C). Further addition of (Li0.5Ce0.5)2+ not only elevated its piezoelectric constant (d33 ∼ 13.3 pC/N) and remnant polarization (Pr ∼ 7.2 μC/cm2) but also increased its high-temperature electrical resistivity (ρ > 108 Ω∙cm at 500 °C and ∼107 Ω∙cm at 600 °C) by more than one order of magnitude when compared with that of other BLSFs. Moreover, the CNBT-LC4 sample maintained 92% of its initial value after depoling at 900 °C and maintained its piezoelectric performance in the following annealing runs. These results demonstrate that Ca0.5(NaBi)0.25-x/2(LiCe)x/2Bi2Ta2O9 ceramics are promising candidates for future applications.

Detailed temperature-dependent structural, dielectric, piezo/ferroelectric, and energy storage properties were explored for the poled (Na0.5-xKxBi0.5-xLax)TiO3 (0 ≤ x ≤ 0.12) ceramics fabricated via a modified sol-gel method. Structural analysis of synchrotron source powder XRD data revealed the rhombohedral (R3c) phase for poled x ≤ 0.03 compositions. Whereas for x ≥ 0.06 samples confirmed structural transition, a mix of rhombohedral and tetragonal (P4bm) phase exists at room temperature. As a function of composition, a rhombohedral phase is found to be suppressed and the tetragonal phase promoted. Dielectric measurements corroborate that at room temperature; dielectric constant was increased with substitution. High-temperature dielectric measurement confirmed the reduction in phase transition temperatures and an increase in the diffuseness of dielectric anomalies with increasing content of K/La. Piezo/ferroelectric measurements revealed that x = 0.03 composition exhibits excellent piezo/ferroelectric properties (piezoelectric coefficient, d33 ∼ 115 pC/N, remnant polarization, 2Pr ∼ 56 μC/cm2, and coercive field, 2Ec ∼ 100 kV/cm) at room temperature. Antiferroelectric ordering improved the energy storage density and efficiency at room temperature (∼0.05 J/cm3, ∼2.6% (for x = 0) to ∼ 0.74 J/cm3, ∼87% (for x = 0.12)) and elevated temperature. For x = 0.06 sample, excellent energy storage density and efficiency ∼1.10 J/cm3 and ∼70% respectively, are obtained at 120 °C. Superior energy storage efficiency showed by x = 0.12 (∼87–∼93%, in the temperature range 30–140 °C) with almost thermally stable energy storage density (from ∼0.74 J/cm3 to ∼ 0.71 J/cm3). These drastic improvements in properties were explained in terms of structural changes as a function of composition and temperature. Observed properties suggest that substituted materials are promising candidates for piezoelectric (for x = 0.03) and energy storage (for x ≥ 0.06) applications.

Magnetoelectric composites have attracted extensive attentions due to the possibility of room temperature coupling effect between the ferroelectric and magnetic phases. We report the comparative study of structure, dielectric, ferroelectric, magnetic properties as well as coupling effect for (1-x)Mn0.5Zn0.5Fe2O4-xBa0.85Sr0.15Ti0.9Hf0.1O3 ((1-x)MZFO- xBSTHO) (x = 0.2, 0.35, 0.5, 0.65, 0.8) composite ceramics prepared by combining coprecipitation process with sol-gel method. The X-ray diffraction result confirm bi-phase structure of the composites, without apparent chemical reaction generated between MZFO and BSTHO. The samples present relative density surface, the mean grain size is in the range of 1–2 μm, which increases slightly with the decrease of molar ratio. The dielectric constant and loss show non-monotonic variation with molar ratio. Temperature and frequency dependence of relaxation peaks are due to the relaxation polarization induced by interface, space charges and weakly bound ions. The peak of the dielectric constant disappears when x is larger than 0.5, while the loss peaks were still observed for all the samples. The remnant polarization increases with x decreasing while the leakage current decreases because the concentration of high-resistance BSTHO is increased. The sample with x = 0.20 shows the largest saturated magnetization of 54 emu/g while the maximal effective saturated magnetization for MZFO is larger than 80 emu/g, obtained at x = 0.65. The coupling coefficient decreases first and then increases, finally it decreases again with the increase of x. The maximal magnetoelectric coupling coefficient is 1420 μV/(cm.Oe), which is obtained for the sample at x = 0.65. The anomalous magnetic and coupling behaviors can be attributed to the strong interface interaction between MZFO and BSTHO.

SrxBa1-xNb2O6 ceramics were prepared via the high-temperature solid-state reaction method. Structural, ferroelectric, electrocaloric effect and pyroelectric energy harvesting capabilities of SrxBa1-xNb2O6 ceramics were reported. The main structural phase of tetragonal tungsten bronze with Sr-doped was detected by X–ray diffraction. It was found that the ferroelectric hysteresis loops became slimmer after the temperature higher than Curie temperature of SrxBa1-xNb2O6 ceramics, which was a representative feature of relaxor ferroelectric. In addition, we presented the positive peak values of electrocaloric at vicinity of Curie temperature which was affected by the applied electric field for all samples. It is worth noting that the pyroelectric energy harvesting property is the first time investigated by using Olsen cycle for SrxBa1-xNb2O6 ceramic. The maximum pyroelectric energy harvesting density was 170 kJ m−3 for x = 0.6 in SrxBa1-xNb2O6 with the temperature range from 293 to 433 K. The experimental results indicated that better pyroelectric energy harvesting property and larger electrocaloric effect of SrxBa1-xNb2O6 ceramic benefited from the higher Sr/Ba ratio. Finally, energy-storage capacity for SrxBa1-xNb2O6 ceramic was obtained from the ferroelectric hysteresis loop and the maximum room-temperature energy-storage efficiency was 86.37% with x = 0.6 under 60 kV cm−1.

The fundamental understanding of polarization switching in ferroelectric materials is very critical for the development of ferroelectric devices. Electric field and temperature induced nanoscale polarization switching has been studied in polycrystalline Bi0.88Sm0.12FeO3 ceramics using piezoresponse force microscopy (PFM). High resolution synchrotron X-ray diffraction, Rietveld refinements and micro-Raman spectra indicate the phase coexistence of rhombohedral R3c and orthorhombic PbZrO3-like structures at room temperature. Temperature dependent Raman spectra exhibit nonpolar Pnma phase-like vibrational bands at 175 °C. The PFM amplitude and phase images revealed irregular multi-grain and domain boundaries with oppositely oriented polarizations which are 180° apart in-phase. Step-wise application of negative and positive tip biases indicates that the 109° polarization switching is more favorable at low fields due to large electric and activation energies associated with 180° switching. PFM in-plane (IP) and out-of-plane (OP) images at different temperatures show the 180° domain growth up to 150 °C. The drastic change in the in-plane phase contrast at 175 °C indicates the formation of 71° ferroelastic domains affirming the phase transition. Temperature dependent phase and amplitude measurements exhibit typical hysteresis and butterfly loops below the transition temperature signifying ferroelectric-like piezoelectric behavior. The sudden decrease in the amplitude value at 175 °C supports a phase transition to non-polar phase where piezoeresponse would be nearly zero. However, there exist non-zero piezoresponse regions at 200 °C implying that ferroelectric clusters are embedded in nonpolar phase which make the material ferroelectrically active at nanoscale level.

Multiferroic Bi(1+x)×0.85Nd0.15FeO3 (BNF) ceramics with various Bi contents are prepared by conventional solid state reaction, and the effects of excess Bi on the structure, morphology, dielectric, ferroelectric, and magnetic properties are investigated. XRD patterns show the coexistence of rhombohedral and orthorhombic phase in all BNF ceramics due to the doping of Nd3+ ions. Bi2Fe4O9 and Bi2O3 impurity can be observed in x = 0 and x = 5%, 7.5% ceramics, respectively. Surface morphologies are closely related to the Bi content and x = 2.5% sample exhibits the largest average grain size of ∼6.72 μm. The leakage current density has been decreased by 3–4 orders of magnitudes through excess Bi. The x = 2.5% sample shows good ferroelectric property with typical hysteresis loop and a large remnant polarization of about 42 μC/cm2 at 150 kV/cm. The P-E hysteresis deteriorates in x = 5% and x = 7.5% ceramics. The PbZrO3-like superstructure related to 1/4(hh0)p diffraction spots in SAED pattern can be found in all BNF ceramics and the number of grain with superstructure observed in each sample decreases as the Bi content increases. As Bi content increases, the remnant magnetization decreases at first, and then increases. Conversion-electron Mossbauer study have ruled out the impacts of Fe2+, Fe4+, or γ-Fe2O3 on the magnetic properties, suggesting that the weak ferromagnetism comes from the destroy of spin cycloid through substitution of Bi3+ ions with Nd3+ ions. Excessive Bi3+ ions have weakened the effect of Nd3+ ions on suppression of spin cycloid and resulted in the degradation of magnetic properties. The slight improvement of magnetic properties in x = 7.5% sample is considered to attribute to Fe vacancies induced by excessive Bi.

The BiMeO3-PbTiO3 (Me = Sc3+, In3+, Yb3+) systems are thought to have remarkable advantage in their Curie temperature in comparison with other perovskite ferroelectric materials. Among them, the BiScO3-PbTiO3 (BS-PT) solid solution with high Curie temperature (450 °C) and excellent piezoelectric coefficient is promising candidate for high temperature sensors and transducers application. Herein, we reported the effect of the addition of Pb(Mn1/3Sb2/3)O3 (PMS) on the electrical properties of BS-PT ceramics. The results showed that the temperature stability of BS-PT ceramics can be improved by the addition of a small quantity of PMS based on conjoint analysis of the temperature dependence of P-E hysteresis loops, leakage current density and kp. While the 0.03PMS-0.33BS-0.64 PT ceramics exhibited the optimal electrical properties at room temperature with the piezoelectric coefficient (d33) of 300 pC/N, the Curie temperature (TC) of 365 °C, the coercive field EC of 17 kV/cm, the dielectric constant er of 1346, and dielectric loss tanδ of 0.74%. It was concluded that the temperature stability of the piezoelectric properties and the relaxor behavior were enhanced by the addition of PMS.

The polycrystalline Bi1-xSmxFe0.97Sc0.03O3 (x = 0.08, 0.12) ceramics have been synthesized using a modified solid-state reaction method. The Bi0.92Sm0.08Fe0.97Sc0.03O3 ceramic possesses single polar rhombohedral R3c phase, while a polar rhombohedral R3c and an anti-polar orthorhombic Pbam phases coexist in the Bi0.88Sm0.12Fe0.97Sc0.03O3 ceramic. The density and the grain uniformity of all the doped ceramics get improved. Further, the addition of Sm and Sc has resulted in significant improvement in ferroelectric characteristics. In addition to this, it also releases the latent magnetization by suppressing the spiral spin structure. The well-defined polarization along the field direction is confirmed by the saturated hysteresis phase loops from 180° domains by piezoresponse force microscopy. The anti-polar Pbam phase experiences a visually electric field induced phase transition to polar R3c phase in the Bi0.88Sm0.12Fe0.97Sc0.03O3 ceramic.

In this work, the detailed ferroelectric properties of pure and yttrium doped 0.64 Pb(Mg1/3Nb2/3)O3-0.36PbTiO3 (Y-doped PMN-PT) ceramics including determination of true remanent polarization and study of resistive leakage were investigated. In dielectric study, the transition temperature (Tm) for the pure and Y-doped ceramic was found to be 205 °C and 165 °C, respectively. Displacement vs. Voltage (D-V) butterfly loops were traced from which a high value of the piezoelectric coefficient for Y-doped PMN-PT (d33 = 604 pm/V) was revealed which was fairly greater than the observed value for pure PMN-PT (d33 = 547 pm/V). The Y-doped PMN-PT ceramic displayed excellent saturated ferroelectric hysteresis loops with higher values of coercive field (Ec), spontaneous (Ps) and remanent (Pr) polarizations, and pyroelectric coefficient (p) compared to the pure PMN-PT ceramic. Also, the Y-doped PMN-PT ceramic displayed good fatigue resistant characteristic indicating its high ferroelectric quality. The relative values of true remanent polarization i.e. Ptr/Pr (in %) were found to be ∼82.86% and 89.60% for pure and Y-doped PMN-PT, respectively using the “Remanent Hysteresis” Task. Also, the resistive-leakage characteristic of both pure and doped ceramics was analyzed using Time-dependent compensated (TDC) hysteresis task. Finally, both pure and Y-doped PMN-PT ceramics have been used for building piezoelectric energy harvesting devices (PEHDs). The Y-doped PMN-PT ceramic based PEHD showed enhanced performance by generating an output voltage around 60 V under periodic mechanical tapping (∼2.0 kgf @ 5 hz) and thus finds application in powering various self-powered devices.

The lack of research on material properties in complex radiation environments has become one of the hindrances to the wider applications of (K,Na)NbO3-based lead-free materials, which is featured with lead free and large piezoelectric coefficients. Hence, in this paper the neutron irradiation characteristics of 0.95(K0.49Na0.49Li0.02)(Ta0.2Nb0.8)O3-0.05CaZrO3 (KNN-LT-CZ) lead-free thin films grown on SrTiO3(001) substrates with La0.67Ba0.33MnO3 and La0.67Ca0.33MnO3 conductive oxide electrodes and metallic Pt electrodes are presented. After neutron irradiation with the dose of 1 × 1014 n/cm2, the KNN-LT-CZ thin films with asymmetric top (Pt) and bottom (conductive oxides) electrodes exhibits a maximum reduction of 6.14% in remnant polarization, and the low-frequency dielectric constant presents a maximum reduction of 51%. While the thin films with symmetric conductive oxides electrodes show less decline in ferroelectric and dielectric properties. Moreover, the leakage current of the films are improved after irradiation. The experimental and analytical results reveal that the KNN-LT-CZ thin films with symmetric La0.67Ca0.33MnO3 electrodes have excellent neutron irradiation resistance.

Single phase Bi3Nb1.125Fe0.0625Co0.0625Ti0.75O9 ceramics with grain-oriented microstructure were prepared using spark plasma sintering. The ferroelectricity was confirmed by the piezoelectric activity of the ceramics measured at room temperature (d33 = 5.6 pC/N). The magnetic measurements evidenced an antiferromagnetic behaviour which can be ascribed to the superexchange interaction of Fe3+-O-Fe3+ and Co3+-O-Co3+. The ferroelectric Curie point and the antiferromagnetic Neel temperature of the ceramic were identified at 1155 K and 153 K, respectively. The material shows multiferroic behaviour below 153 K.

Ilmenites, which find enormous applications, because of their high relative permittivity and modest dielectric losses can have their efficiency and practical applicability enhanced by incorporation of ferroelectricity and multiferroicity in them. In our present work, ferroelectricity and magneto-electric (ME) effect is induced in the non-ferroelectric ilmenite FeTiO3 by modifying it with bismuth and lead titanate. The structural, micro-structural, electrical, ferroelectric and magneto-electric effect of the studied compounds were investigated using x-ray diffraction, field emission scanning electron microscope, phase sensitive impedance analyser, polarization–electric field hysteresis loop measurements and ME set up respectively. The analysis of I ∼ V characteristics curve shows that the modification results in the decrease of leakage current of the parent compound by three order of magnitude. Thus, in the present work, it is shown that the modifications not only induce ferroelectricity and multiferroicity in the parent compound, but also reduces the leakage current drastically.

A large electrostrain usually occurs at ferroelectric-ferroelectric phase boundaries. However, in the Ba(Ti1 – xZrx)O3 (BT-xZr) system prepared by the conventional solid-state reaction method, we discovered a local electrostrain maximum in the single rhombohedral phase region at the quasi-quadruple point with a composition of BT-0.12Zr that had a relatively weak temperature sensitivity below 50 °C. Mechanisms of the local electrostrain maximum in the single-phase region of the BT-xZr system were studied. The large coercive field and large domain size of BT-0.12Zr indicate that domain switching was not facilitated. Nevertheless, the large lattice distortion of BT-0.12Zr suggests a large intrinsic lattice strain, which predominantly contributed to the observed macroscopic electrostrain enhancement at the quasi-quadruple point composition in the single-phase region. Compared to nearby sample compositions, the largest lattice distortion of BT-0.12Zr was found to be correlated with the highest electrostrictive coefficient at the tricritical quasi-quadruple point, as deduced from phenomenological Landau analysis. Our work may shed light on the development of weakly temperature-dependent large electrostrain materials by identifying the tricritical quasi-quadruple point in ferroelectric phase diagrams.

The electrical poling of piezoceramics is an essential process, to maximize their piezocoefficient prior to applications, which can significantly alter their other physical properties. In this study, the effect of poling on the properties of lead free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 exhibiting large piezocoefficient was investigated. The sample revealed octahedral distortion induced structural transformation upon poling. The impedance spectrum displayed the resonance modes in poled state, where maximum power transmission is feasible. The polarization hysteresis loop exhibited an asymmetry with an internal bias electric field of 41 V/mm due to the field induced orientational defect. The strain measurements revealed 50% enhancement in electrostriction for the sample after poling. Additionally, the sample revealed an incremental change in bandgap due to B-site cationic off-centre displacements induced by the octahedral distortion. Importantly, the poling induced large internal bias field and the near UV bandgap of the sample facilitated the observed large photovoltaic response with giant open circuit voltage of 18 V which could open up an additional application in the fields such as photovoltaic and UV detector for this versatile compound.

We present the study of structural, morphological, dielectric, transport and ferroelectric properties of (1-x)BFO–xPTO solid solutions, with 0.3 ≤ x ≤ 0.6, prepared via non-conventional synthesis methods. These methods include Sol-gel and Single-step solid state method. Structural analysis revealed presence of mixed phases i.e. monoclinic (CC) and tetragonal (P4mm) phases, for all compositions showing a Morphotropic Phase Boundary. For the compositions with higher concentration of PTO, an increase in tetragonal phase fraction has been observed. Quantitative analysis showed, in general, higher value of c/a (i.e. tetragonality) for all samples as compared to the bulk PTO. The morphological analysis shows small grain size irrespective of synthesis method and composition. The low temperature frequency dependent tangent loss shows dielectric relaxation with small magnitude of dielectric constant indicating absence of extrinsic contributions. High temperature dielectric anomaly is observed around 400–500 K corresponding to magnetic phase transformation of BFO at Neel temperature which suggest the presence of magneto-electric coupling in specific compositions. Sol-gel prepared composite appeared to be more resistive than the Single-step synthesized composite and shows Arrhenius type dependence of high temperature ac conductivity. Ferroelectricity was observed in all ceramic samples which sustained high applied electric field up to 190 kV/cm. Finally, a correlation between polarization, tetragonal phase fraction and c/a ratio, has been drawn and discussed. It is concluded that c/a ratio (i.e. tetragonality) is more important parameter which can be tuned to achieve enhanced ferroelectric response as compared to the tetragonal phase fraction in (1-x)BFO–xPTO solid solutions.

Single-crystal heterostructured multiferroic (PbTiO3) PTO-(CoFe2O4) CFO nanoplate composites were prepared by a simple two-step hydrothermal process. The CFO nanoparticles with the size of 20–80 nm selectively grow on the positively polarized surface of the single-crystal and single-domain PTO nanoplate. The TEM results demonstrate an epitaxial growth relation between the PTO nanoplates and CFO nanoparticles. The results of the temperature-dependence magnetization of the composites under zero field cooled (ZFC) condition show a novel broad diffuse region around the PTO ferroelectric phase transition (Tc) for the first time. The total change of magnetization (Δ M) near Tc is determined to be (2.71 ± 0.5) × 10−3 emu, a change of 46.2%, implying a giant magnetoelectric coupling in these single-crystal heterostructured multiferroic PTO-CFO nanoplate composites. Such effect has been attributed to the absence of the substrate clamping and single domain in ferroelectric PTO nanoplate.

CuO-added 0.96(LixNa0.5-xK0.5)(Nb1-ySby)O3-0.04SrZrO3 ceramics were sintered at 1020 °C for 6 h. Various crystal structures were synthesized in these specimens by controlling the Li2CO3 (x) and Sb2O5 (y) contents: pseudocubic, orthorhombic-pseudocubic polymorphic phase boundary (PPB), tetragonal-pseudocubic PPB, orthorhombic-tetragonal-pseudocubic PPB, and orthorhombic-tetragonal PPB structures. The pseudocubic structure developed in these specimens was similar to the R3m rhombohedral structure instead of the Pm3m cubic structure because the specimens with a pure pseudocubic structure showed good ferroelectric and piezoelectric properties. The piezoelectric properties of the specimens were influenced by their crystal structures. The specimen with the tetragonal-pseudocubic PPB structure showed the best piezoelectric properties because this structure was similar to the tetragonal-rhombohedral morphotropic phase boundary structure developed in Pb(Zr1-xTix)O3-based ceramics. In particular, the specimen with the tetragonal-pseudocubic PPB structure corresponding to x = 0.05 and y = 0.065 showed the largest d33 and kp values of 431 pC/N and 0.43, respectively.

Ferroelectric 0.7BiFeO3-0.3PbTiO3 (BFO-PT) thin films were deposited on LaNiO3 (LNO) coated stainless steel (SS) substrates by the sol-gel method. XRD results indicate that both LNO and BFO-PT thin films have the perovskite structure and the film crystallinity is improved with increasing the LNO thickness. The dielectric loss of BFO-PT thin films is reduced significantly with addition of LNO buffer layers, achieving about 4% at the frequency of 1 kHz, much lower than that of >20% for BFO-PT thin films directly deposited on SS substrates. BFO-PT thin films reveal the strong ferroelectricity with remnant polarization (Pr) of about 35 μC/cm2 for LNO of 390 nm. Moreover, addition of LNO buffer layers mitigates the polarization deterioration after the 1.33 × 108 switching cycles resulting in the improved anti-fatigue properties of BFO-PT thin films. Our results indicate that BFO-PT/LNO multilayer thin films on SS substrates maintain excellent dielectric and ferroelectric properties.

We prepared two-dimensional close-packed hemispherical CoFe2O4(CFO)/Pb(Zr0.52Ti0.48O3)(PZT)/LaNiO3(LNO)/NiO thin film on Si(100) substrate using a template made of monodispersed polymethyl methacrylate (PMMA) particles. LNO and NiO layers are introduced for the bottom electrode and seed to crystallize, respectively. Since this hemispherical thin film is connected with the substrate only at the “foot” of the hemisphere, this thin film has a hollow structure. Therefore we call this structure as “free-standing” thin film. In this work, we also prepared planar CFO/PZT/LNO/NiO thin film on Si(100) substrate without using the PMMA template for comparison. In this work, we examined the effect of applying a vertical external magnetic field on the ferroelectric property. It was found that applying an external magnetic field decreases remanent polarization (Pr) for both planar and free-standing thin film. The degree of decrease of Pr in the free-standing thin film is about four times larger than that in the planar thin film. This indicates that large multiferroic property (interaction between ferromagnetic and ferroelectric) is realized in the free-standing thin film.

Multiferroic Dy and transition metals (Cr, Mn, Ni) co-doped BiFeO3 ceramics were successfully synthesized by a solid-state method, and the influence on the magnetic and ferroelectric properties were investigated. Compared with Bi0.95Dy0.05Fe0.95Mn0.05O3, Bi0.95Dy0.05Fe0.95Cr0.05O3 and Bi0.95Dy0.05Fe0.95Ni0.05O3 ceramics can significantly improve the magnetic properties. The significant enhancement of magnetic properties should be related to the local ferromagnetic coupling from Cr ions (Ni ions) and Fe ions, which have already been proved by first-principles calculations. Meanwhile, both experimental and theoretical studies reveal the Dy substitution can effectively enhance the ferroelectric properties of BiFeO3. Leakage current and conduction mechanism analyses reveal that the improved ferroelectric properties are mainly attributed to the reduced oxygen vacancies.

Solid solution of Ca10.5–1.5xYbx(PO4)7 (0 ≤ x ≤ 1) was synthesized in the β-Са3(РО4)2-type structure by a standard solid-state method. Second-harmonic generation, differential scanning calorimetry, and dielectric measurements showed the presence of a reversible first-order phase transition of ferroelectric type between the room-temperature polar R3c structure to centrosymmetry. The temperature of the phase transition decreases from 1203 K for x = 0 to 788 K for x = 1, while the second-harmonic generation response decreases from 1.4 to 0.17 α-SiO2 powder standard units. The luminescence spectra of Ca10.5–1.5xYbx(PO4)7 point to two structural Yb3+ positions in full agreement with the structural data. The intensity of the luminescence emission line at ∼975 nm due to the 2F5/2 → 2F7/2 transition reaches the maximum at x = 0.667 in Ca10.5–1.5xYbx(PO4)7. The Yb3+ luminescence spectra studied as a function of the chemical composition 0

This study reports influences of Sm doping on the crystal structure, nanomechanical and ferroelectric properties of Bi1-xSmxFeO3 (BSFO) thin films. BSFO films of perovskite phase were deposited on Pt/glass substrates by pulse laser deposition (PLD). The structural analysis shows that the BSFO transforms from rhombohedral structure into orthorhombic structure with the phase boundary near x = 0.16. The structure morphology of the thin films determined by using SEM and AFM exhibited that the grain size and surface roughness are reduced with increasing Sm content in BSFO. The hardness and Young's modulus are obtained in the range of 7.7–10.1 GPa and 154.6–167.5 GPa, respectively. Ferroelectric properties with remanent polarizations (2Pr) and coercive fields (Ec) occur respectively in the ranges of 41–150 μC/cm2 and 327–450 kV/cm for x = 0.05–0.14. The enhanced ferroelectric properties can be attributed to the smooth interface and fine microstructure with small grain sizes in range of 30–200 nm. A double ferroelectric hysteresis P-E loop with a different nanomechanical properties is observed in the composition of x = 0.16 and is associated with the appearance of orthorhombic phase. The leakage behavior with mechanisms and nanomechanical characterizations are also studied as functions of Sm content.