O3 Matrix Research Articles

Electrocaloric response enhancement over a broad temperature range in lead-free BT-based ceramics

The electrocaloric effect (ECE) capabilities of environmentally sustainable BaTiO3 systems have garnered extensive scrutiny for their potential applications, owing to their intricate phase transition characteristics, facile miniaturization, heightened efficacy, and low cost. Nevertheless, persistent challenges loom in the quest for a substantial trade-off between significant temperature change (ΔT) and a wide operating temperature range (Tspan). In this study, we synthesized the Ba(1–1.5x)LaxTi0.9Zr0.1O3 (abbreviated as BLZT100x, x = 0, 0.005, 0.01, and 0.015) ferroelectric system and conducted thorough characterizations encompassing phase structure, electrical attributes, and electrocaloric properties. The results reveal a reduction in the phase transition temperature to lower regimes and an augmentation in the diffuse phase transition characteristics upon the incorporation of La3+ into the Ba(Zr, Ti)O3 matrix. This enhancement significantly bolsters the electrocaloric performance while expanding the viable operating temperature ranges. Notably, in the BLZT0.5 sample, an exceptional ΔT of 1.22 K under a moderate electric field of 50 kV/cm is observed, accompanied by an extraordinarily broad Tspan of 80 °C spanning from 60 °C to 140 °C, as determined through direct measurement method. These findings impeccably align with the prerequisites of practical refrigeration applications.

Pyrolysis of Al-Based Metal-Organic Frameworks to Carbon Dot-Porous Al2 O3 Composites With Time-Dependent Phosphorescence Colors for Advanced Information Encryption.

Phosphorescent materials with time-dependent phosphorescence colors (TDPCs) have great potential in advanced optical applications. Synthesis of such materials is attractive but challenging. Here, a series of carbon dot-porous Al2 O3 composites exhibiting distinctive TDPC characteristics is prepared by high-temperature pyrolysis of Al-based metal-organic frameworks NH2 -MIL-101(Al). The composite synthesized at 700 °C (CDs@Al2 O3 -700) shows an obvious change in phosphorescence color from blue to green after removing the excitation light of 280nm. Photophysical analysis reveals that two emission centers in CDs, namely carbon core and surface states, are responsible for the short-lived blue phosphorescence (96ms) and long-lived green phosphorescence (911ms), respectively. The combination of blue and green phosphorescence with different decay rates triggering the interesting TDPC phenomenon. CDs@Al2 O3 -700 has a significantly high phosphorescence quantum yield of up to 41.7% and possesses an excellent optical stability against water, organic solvents, and strong oxidants, which benefits from the multi-confinement of CDs by the porous Al2 O3 matrix through rigid network, strong space constraint, and stable covalent bonding. Based on the TDPC property, multilevel coding patterns composed of CDs@Al2 O3 are successfully fabricated for advanced dynamic information encryption.

Field-induced strain engineering to optimize antiferroelectric ceramics in breakdown strength and energy storage performance

The unique filed-induced phase transition makes antiferroelectric (AFE) ceramics naturally advantageous in exploiting advanced capacitors with ideal energy storage performance. However, low breakdown strength (BDS) has become one key restriction on energy storage performance of AFE ceramic and there have fewer research been carried out focused on optimizing breakdown strength with the design strategy based on regulating field-induced strain behavior. Here, we first propose introducing Nd3+ to induce incommensurate modulated AFE phase in Pb0.98Sr0.02Zr0.75Sn0.25O3 (PSrZS) matrix. Benefited from this strategy, the field-induced strain was well dispersed that the strain rate under electric field (strain/electric field) significantly decreased. Accordingly, inducing incommensurate modulated AFE phase in matrix by introducing Nd3+ greatly enhanced the BDS from 350 kV/cm to 540 kV/cm by regulating strain behavior combined with the delayed saturated polarization and significantly optimized several key parameters including hysteresis width and phase-switching field. As a result, outstanding recoverable energy density of 14.21 J/cm3 accompanying with high efficiency of 87.35% were obtained in 0.03 Nd-doped PSrZS ceramics at 530 kV/cm at room temperature. The actual discharge performance is also prominent. Ultrahigh current density of 2111 A/cm2 and power density of 507 MW/cm3 were obtained in PSrNd0.03ZS ceramics. The sample also exhibited a high discharge energy density of 9.11 J/cm3. The great energy storage properties obtained in this work provides a novel strategy to further enhance the energy storage performance and demonstrates the extremely potential of AFE ceramics in exploiting advanced ceramic capacitors for pushing on the miniaturization and integration of electronic devices.

Superb Energy Storage Capability for NaNbO3 -Based Ceramics Featuring Labyrinthine Submicro-Domains with Clustered Lattice Distortions.

Designing superb dielectric capacitors is valuable but challenging since achieving simultaneously large energy-storage (ES) density and high efficiency is difficult. Herein, the synergistic effect of grain refining, bandgap widening, and domain engineering is proposed to boost comprehensive ES properties by incorporating CaTiO3 into 0.92NaNbO3 -0.08BiNi0.67 Ta0.33 O3 matrix (as abbreviated NN-BNT-xCT). Apart from grain refining and bandgap widening, multiple local distortions embedded in labyrinthine submicro-domains, as indicated by diffraction-freckle splitting and ½-type superlattices, produce slush-like polar clusters for the NN-BNT-0.2CT ceramic, which should be ascribed to the coexisting P4bm, P21 ma, and Pnma2 phases. Consequently, a high recoverable ES density Wrec of ≈ 7.1Jcm-3 and a high efficiency η of ≈ 90% at 646kVcm-1 is achieved for the NN-BNT-0.2CT ceramic. Such hierarchically polar structure is favorable to superb comprehensive ES properties, which provide a strategy for developing high-performance dielectric capacitors.

Hierarchically polar structures induced superb energy storage properties for relaxor Bi0.5Na0.5TiO3-based ceramics

Electrostatic capacitors are fundamental components in electronics and electric power systems because of their inherent superiorities of charging/discharging speed and power density. However, energy storage properties (ESPs) of the top promising relaxor ferroelectric (RFE) are intimately entwined symmetry of local lattice and dynamics of nano-scaled polar structure. Herein, hierarchically polar structure and oxygen octahedral tilting can be induced in the 0.7Bi0.5Na0.5TiO3-0.3Na0.91Bi0.09Nb0.94Mg0.06O3 (BNT-NBNM) matrix with the addition of CaZrO3 (CZ) to achieve outstanding comprehensive ESPs. The chemically induced coexisting triple phases of tetragonal P4bm, orthorhombic P21ma and Pnma2 bring forth hierarchically polar structure, featuring nanodomains and slush-like polar clusters embedded in stripe submicro-domains, as indicated by morphological observations, splitting of diffraction spots and polar state distributions. Accordingly, an ultrahigh recoverable energy storage density Wrec = 7.5 J cm−3 concurrent with a high-efficiency η = 94.5 % at a breakdown electric field of 510 kV cm−1 can be attained in BNT-NBNM-0.05CZ RFE ceramic. In addition, the optimal composition also displays excellent stability (Wrec = 5.1 ± 0.1 J cm−3, η = 92.7% ± 1%, 20–170 °C and Wrec = 5.2 ± 0.2 J cm−3, η = 92.1% ± 1.3%, 5–500 Hz) at 410 kV cm−1. The present work provides a new perspective for designing lead-free RFE ceramics with ultra-high ESPs that benefit from hierarchically polar structures.

Alkali-earth metal ion inducing multiphase transition of lanthanum-free Pb(Zr0.5Sn0.5)O3 ceramics improves the energy storage properties

Constructing the stepwise phase transition can delay the polarization process of antiferroelectric ceramics, possessing certain significance for improving the energy storage density. However, the common multiphase transitions are obtained in the rare-earth ions doped PbZrO3-based systems. In the present work, the multiphase transition can also be induced in the lanthanum-free Pb(Zr0.5Sn0.5)O3 matrix with mere doping of the alkali-earth metal ion Sr. The introduction of Sr endows the matrix with a higher lattice distortion and the reduced phase-transition temperature. Moreover, related to the induced stepwise electric field-induced phase transition, the energy storage properties are remarkably enhanced to 10.5 J/cm3 and 83.2% when the substitution content of Sr is 3 mol. %. Sr modification can adjust the phase structure by regulating the phase stability of the matrix and suppress the leakage current originating from the structural changes. This work provides a successful attempt that the phase structure and energy storage performance of antiferroelectric ceramics can also be effectively controlled through cheaper and simpler element modification. The optimized energy storage performance provides a new material selection for pulsed power devices.

Realizing high energy density in BiFeO3-based ceramics capacitors via bandgap engineering and polarization optimization

BiFeO3-based lead-free ferroelectrics possess high spontaneous polarization. Nevertheless, achieving ultrahigh recoverable energy density in BiFeO3-based ceramics is limited by large remanent polarization and insufficient breakdown strength. Herein, (0.7-x)BiFeO3-0.3Ba(Hf0.05Ti0.95)O3-xNaTaO3 ceramics were designed and prepared. It exhibited a high recoverable energy density of 6.3 J/cm3 and high efficiency of 86.6 % due to the contribution of large breakdown strength and optimized polarization (high maximum polarization and small remanent polarization). These contributions stem from NaTaO3 being introduced into the 0.7BiFeO3-0.3Ba(Hf0.05Ti0.95)O3 matrix, which successfully brought in widened bandgap Eg, increased resistivity, and enhanced relaxor behavior. Large breakdown strength is also promoted by dense microstructure and decreased average grain size. This work proves that the strategies of bandgap engineering and polarization optimization for improving energy storage performance in BiFeO3 are practicable.

Simultaneously achieving high energy storage performance and low electrostrictive strain in BT‐based ceramics

AbstractDielectric ceramics with high recoverable energy storage density (Wrec) and high energy storage efficiency (η) are urgently needed due to their potential application in pulse capacitor devices. However, the low η and breakdown strength (BDS) have produced a bottleneck for achieving high Wrec at high electric field. Here, we introduce Bi(Mg0.5Ti0.5)O3 (BMT) into Ba(Ti0.92Sn0.08)O3 (BTS) matrix to enhance the relaxor character of BTS–xBMT and reduce the electrostrictive strain generated during electric field loading. The enhanced relaxor character is beneficial for increasing the efficiency, whereas the reduced electrostrictive strain is profitable to increase the BDS. Furthermore, the BDS is significantly improved by the polymer viscous rolling process. Finally, the electrostrictive effect was considerably lowered in an optimized BTS–0.1BMT composition. More crucially, a high Wrec of 4.34 J/cm3 was attained accompanied by excellent temperature stability (variation ≤±5% between 30 and 120°C). The current results show that the developed dielectric ceramics can be used in pulse capacitor devices for energy storage.

Effect of calcination temperature on the structural and electrical properties of low temperature sintered the (Na0.52K0.44Li0.04)(Nb0.88Sb0.08Ta0.04)O3 textured ceramics

The 1.5 mol% Na2O excess (Na0.52K0.44Li0.04)(Nb0.88Sb0.08Ta0.04)O3 (NKN-LST) matrix powders were calcined at 500–950 °C. A perovskite structure of calcined powders without crystallinity obtains calcined at 550 °C. As the calcination temperature increases to 750 °C, NKN-LST powders have a single orthogonal structure. When the calcination temperature ≥800 °C, NKN-LST powders form tetragonal structure. In the calcination temperature range of 800–900 °C, it can be seen that there exists a two-phase coexistence of orthogonal and tetragonal structure in NKN-LST powders. Highly textured (001)-NKN-LST were prepared by the templated grain growth (TGG) using a two-step thermal process with Na2O as a low temperature sintering aid. And the texture and properties of NKN-LST textured ceramics have a great influence on the calcination temperature of matrix materials. The optimum electrical properties of NKN-LST ceramics with an orientation degree of 98.9%, a d 33 of 442 pC/N, a k p of 0.58, an ε 33 T of 2935, were calcined at 750 °C, sintered for 1115 °C, 8 h. Therefore, the reduction of calcination temperature induces a significant advancement of 1.5 mol% Na2O excess NKN-LST textured ceramics.

Enhancing catalytic activity of CO2 electrolysis via B-site cation doped perovskite cathode in solid oxide electrolysis cell

Solid oxide electrolysis cell (SOEC) is considered as a high energy-efficient CO2 conversion method and a promising technology to achieve carbon neutralization. Thus, in this work, the reduced Co or Ni doped Pr0.4Sr0.6Fe0.9Mo0.1O3 perovskite oxides are used as the cathode of SOEC. After reduction, Co-Fe alloy nanoparticles are in situ exsolved from Pr0.4Sr0.6Co0.2Fe0.7Mo0.1O3 and Pr0.4Sr0.6Co0.45Fe0.45Mo0.1O3, and NiFe10.8 alloy nanoparticles are attached on the Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 matrix. The reduced Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 exhibits the highest oxygen vacancy concentration and CO2 adsorption ability, which further promote oxygen surface exchange and electrochemical surface exchange reaction. Besides, the reduced Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 exhibits the highest surface reaction rate constant (kchem) of 3.54 × 10-4 cm s-1 and highest oxygen chemical bulk diffusion coefficient (Dchem) of 27.53 × 10-5 cm2 s-1, suggesting that reduced Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 shows the best catalytic activity for CO2 reduction reaction. The symmetrical cell with reduced Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 shows the lowest polarization resistance (Rp) value, and at 800 °C, the electrolysis cell with reduced Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 cathode also exhibits the best performance of 0.81 A cm-2 in 50%CO-50%CO2 and 1.05 A cm-2 in pure CO2 at 1.5 V, indicating that reduced Pr0.4Sr0.6Ni0.2Fe0.7Mo0.1O3 is a promising cathode for CO2 electrolysis.

Insight into Key Parameters for Fabricating Stable Single-Atom Pt-Nix Alloy by Reduction Environment-Induced Anti-Ostwald Effects.

Developing single-atom catalysts with superior stability under reduction conditions is essential for hydrogenation/dehydrogenation catalysis and green hydrogen generation. In this contribution, single-atom Pt catalysts were achieved via a reduction environment-induced anti-Ostwald approach in the highly confined Ni species (Pt-Nix ) on nonreducible Al2 O3 matrix. In-situ X-ray absorption spectroscopy indicated that the isolated Pt-Nix metallic bonds, generated at high reduction temperature, dominated the formation of single Pt atoms. A relatively large cluster of metallic Ni would benefit the stabilization of Pt single atom as observed via high-angle annular dark-field scanning transmission electron microscopy and validated by density functional theory simulation. Excellent performance on cellulose hydrogenolysis was demonstrated under harsh reductive and hydrothermal conditions, potentially expandable to other hydrogen involved reactions like CO2 hydrogenation, green hydrogen production from different hydrogen carriers, and beyond.

Rare earth free oxide nano-composite of SrTi0.85Nb0.15O3 and CNT for potential n-type thermoelectrics

Despite having large electron concentration, the electrical conductivity of Nb doped SrTiO3 severely suffers from poor carrier mobility. Even after taking several attempts by different research groups, it is still challenging to improve carrier mobility without affecting the Seebeck coefficient. In this report, 1-dimensional CNT has been introduced in SrTi0.85Nb0.15O3 (STN) matrix to fabricate STN + CNT nano composites as CNT is expected to have boosted the mobility by several orders. We have reported more than 1000 % increase in electrical conductivity after CNT addition. In contrast, Seebeck coefficient remains flat with CNT loading. This remarkable enhancement of electrical conductivity accompanied by essentially no change in thermopower leads to a 380% increase in the ZT parameter. Although CNT has been previously introduced in chalcogenides, binary oxides, and oxy-chalcogenides, such a remarkable surge in electrical transport with the incorporation of a small amount of CNT has never been reported. Moreover, to the best of our knowledge, this is the first report on thermoelectric properties of oxide perovskite composites with CNT. Our results suggest that forming oxide-CNT nano-composites can be a robust strategy to improve the thermoelectric performance in bulk materials for realistic applications.

Significant improvement in electrical characteristics and energy storage performance of NBT-based ceramics

Dielectric capacitors with superior power density and ultra-fast charge/discharge capability have attracted growing attention in the pulse power field. In this work, rare earth oxide (Sm2O3) was introduced into (0.74Na0.5Bi0.5-0.26Sr)Ti0.9Zr0.1O3 matrix, to enhance the comprehensive energy storage performance. The structure, dielectric and ferroelectric characteristics of these materials were systematically studied, to assess the potential application in multilayer ceramic capacitors. All samples yielded a perovskite structure, as the addition of Sm2O3 results in a substantial increase in density, along with the enhancement of relaxor behavior and local nanodomains. With increasing Sm2O3 concentration, a distinctly slim ferroelectric hysteresis loop as well as frequency dispersive dielectric characteristics have been detected. The NBSZT-0.02Sm ceramic has realized an excellent energy storage density of 4.62 J/cm3, with a moderately good energy efficiency of 84.38% and favorable temperature stability over a broad temperature range of 102.7–397.1 °C. The activation energy (Ea) of the ceramics increased from 1.40 eV to 1.72 eV with Sm2O3 concentration increasing from x = 0 to x = 0.04, which inhibits the appearance of the local electrical branch and thus improves the breakdown strength of the NBSZT-xSm ceramics. This study provides a novel possibility for designing lead-free ceramic materials for high-temperature capacitors.

Investigation of the structural, optical and dielectric properties of La-doped BaTi0.97Y0.03O3 ceramic

A series of Lanthanum (La)-doped BaTi0.97Y0.03O3 ceramics were successfully prepared using the sol gel process and their structural, microstructural, optical and dielectric properties investigated. The X-ray diffraction (XRD) patterns of all the as-prepared samples showed a tetragonal phase without the presence of any secondary phase which was also confirmed by Rietveld refinement. Raman spectroscopy analysis revealed the appearance of the A1g mode, which can be considered as the signature of the co-doping with La at the Ba-sites and Y at the Ti-sites in the BaTiO3 matrix. Scanning electron microscopy (SEM) analysis revealed a decrease in grain size with the incorporation of La into the BaTi0.97Y0.03O3 matrix. Ultraviolet–Visible (UV–Vis) spectroscopy results showed that La did not significantly influence the band gap energy of the BaTi0.97Y0.03O3 matrix and therefore it preserved its insulating character in contrast to other dopants (Iron, Samarium) as reported in the literature. Dielectric measurements showed that doping with La lowered both the temperature value of the maximum of the permittivity (Tm = 44 °C for x = 5% at 10 kHz) and of the dielectric losses (tan δ < 0.02 for x = 3% at 10 kHz). Moreover, a weak positive temperature coefficient of resistivity (PTCR) effect was observed on the Lanthanum doped samples for the two compositions x = 1% and 3%.

Self-assembled growth and magnetic properties of Fe and FeTiO3 core–Sr(Ti,Fe)O3 shell nanocomposites

In this study, a promising method for the modulation of the microstructure, composition, and magnetic properties of thin films fabricated by co-sputtering metallic Fe and oxide SrTiO3 targets is proposed. The proposed method can potentially be applied in multifunctional electronics. The flat surface morphology was observed in the thin film sputtered under a low power for the Fe target, whereas micro-height rods were fabricated on an uneven layer at a higher power. Strong magnetic anisotropy was not observed in the co-sputtered thin films because of the randomly oriented growth of the magnetic rods. Detailed microstructural and compositional studies using high-resolution transmission electron microscopy and scanning transmission electron microscopy revealed that self-assembled nanocomposites with three components were grown with a core–shell structure, in which Fe and FeTiO3 phases grew in the Sr(Ti,Fe)O3 matrix. This report provides an insight into designing multifunctional metal–metal oxide nanocomposites with single-step co-sputtering, which is capable of adjusting the composition and geometry of the nanocomposites.

One doping strategy to simultaneously lower the sintering temperature and increase the energy storage properties

Antiferroelectric (AFE) ceramics with low sintering temperature are of great importance to the application in the Multilayer ceramic capacitors (MLCC). However, conventional method of adding sintering aids will introduce the grain boundary glass phases with low dielectric constant, which is limited in the property enhancement. Thereby new way to simultaneously obtain low sintering temperature and superior performance improvement are urgently needed. Herein, a novel strategy of letting metal cation enter the lattice to avoid the above disadvantages was proposed and one specific attempt was carried out by adding Bi2O3 as raw material instead of sintering aids to introduce Bi3+ into the (Pb0.98Sr0.02)(Zr0.6Sn0.4)O3 matrix. For all samples containing Bi3+, low sintering temperature of ∼ 1100 °C and outstanding performance improvement are simultaneously achieved. With small amount of Bi3+, the recoverable energy density is prominently enhanced from 7.78 J/cm3 to 11.28 J/cm3 accompanying with high energy efficiency of 85.54%. Meanwhile, outstanding practical discharge performance of ultrahigh current density of 2144 A/cm2 and power density of 332 MW/cm3 can be also achieved. Results testify that the introduction of Bi3+ in lattice truly lowers the sintering temperature and thus densifies the microstructure, maintains high polarization characteristic and promotes the stability of the AFE phase. The proposed novel and effective strategy to further design the dielectric ceramics with low sintering temperature and superior energy storage performance is of great instructive significance for the further development of MLCC and other advanced ceramic capacitors.

Tailored Fabrication of Carbon Dot Composites with Full-Color Ultralong Room-Temperature Phosphorescence for Multidimensional Encryption.

Ultralong room‐temperature phosphorescence (RTP) is highly useful for information encryption, organic electronics, bioelectronics, etc. However, the preparation of related metal‐free materials with multiple colors across the full spectrum remains a major challenge. Herein, a facile method is developed to fabricate boron‐doped carbon dot (B‐CD) composites with full‐color long lifetime RTP continuously tailorable in the range of 466–638 nm simply by pyrolysis of the citric acid and boric acid precursors with various mass ratios at different temperatures. This leads to the formation of luminescent B‐CD centers in a rigid polycrystalline B2O3 matrix, which effectively stabilizes the triplet excited states of B‐CDs. Thus, the composites become phosphorescent over a relatively long period (5–12 s) after the removal of the irradiation source. Meanwhile, the increased particle size and oxidation degree of B‐CDs obtained at larger citric acid feeding or higher pyrolysis temperature continuously shift the phosphorescence from blue to red. Due to the formation of multiple luminescence centers, the RTP can also be finely modulated by the excitation wavelength. The resulting B‐CD composites with highly tunable long lifetime RTP further allow a variety of distinctive applications in multidimensional encryption handily utilizing space, time, and color variations.

Resolving atomic-scale phase transformation and oxygen loss mechanism in ultrahigh-nickel layered cathodes for cobalt-free lithium-ion batteries

Summary Doped LiNiO2 has recently become one of the most promising cathode materials for its high specific energy, long cycle life, and reduced cobalt content. Despite this, the degradation mechanism of LiNiO2 and its derivatives still remains elusive. Here, by combining in situ electron microscopy and first-principles calculations, we elucidate the atomic-level chemomechanical degradation pathway of LiNiO2-derived cathodes. We uncover that the O1 phase formed at high voltages acts as a preferential site for rock-salt transformation via a two-step pathway involving cation mixing and shear along (003) planes. Moreover, electron tomography reveals that planar cracks nucleated simultaneously from particle interior and surface propagate along the [100] direction on (003) planes, accompanied by concurrent structural degradation in a discrete manner. Our results provide an in-depth understanding of the degradation mechanism of LiNiO2-derived cathodes, pointing out the concept that suppressing the O1 phase and oxygen loss is key to stabilizing LiNiO2 for developing next-generation high-energy cathode materials.

Structural and dielectric properties of sol–gel processed Ce-doped BaTi0.97Y0.03O3 ceramics

Structural and dielectric properties of Ce-doped [Formula: see text][Formula: see text]O3 powders, with the chemical formulation (Ba[Formula: see text][Formula: see text](Ti([Formula: see text]- [Formula: see text]O3 such as [Formula: see text] = 0%, 1%, 3%, 5%, 7% and 9%, produced by the sol–gel method, have been investigated. X-ray diffraction analysis showed that Ce[Formula: see text] ions incorporated Ba sites until [Formula: see text]= 7% indicating that this concentration represents a solubility limit of Ce[Formula: see text] ions in [Formula: see text][Formula: see text]O3 matrix. Scanning electron microscopy (SEM) analysis showed a decrease in grain size down to the same concentration of 7%. Raman spectroscopy analysis showed the appearance of [Formula: see text] mode, which we attributed to the effect of incorporation of Ce[Formula: see text] and Y[Formula: see text] in BaTiO3 matrix. Dielectric measurements revealed that doping with cerium lowers the temperature of permittivity maximum at the ferroelectric-to-paraelectric transition (FPT) of the [Formula: see text][Formula: see text]O3 sample, and reaches a value that should be below [Formula: see text]C for [Formula: see text]= 9%. Moreover, the phenomenon of dielectric resonance was observed on all Ce-doped samples, which was not the case with other dopants as reported in the literature.

Lead palladium zirconate titanate: A room temperature nanoscale multiferroic thin film

The discovery of single-phase multiferroic materials and the understanding of intriguing physics of the coupling mechanisms between their spin and polarization are important for the next generation of multifunctional devices. In this work, we report dielectric, ferroelectric, and magnetization results of Pd-substituted room-temperature magnetoelectric multiferroic Pb(Zr0.20Ti0.80)0.7Pd0.3O3 (PZTPd) thin films. Highly c axis oriented PZTPd thin films were grown on {(LaAlO3)0.3(Sr2AlTaO6)0.7} substrates using the pulsed laser deposition technique. These films were phase pure and stabilized in a tetragonal phase. Atomic force microscopic studies indicated a homogeneous distribution of grains on the films' surface with a surface roughness (RQ) of ∼5.4 nm. A large dielectric constant of ∼1780 and a low loss tangent value of ∼0.52 were observed at 1 kHz measured at room temperature. Temperature dependent dielectric studies on Pt/PZTPd/La0.7Sr0.3MnO3 metal–insulator–metal heterostructure capacitors between 80 and 660 K indicated a diffused ferroelectric to paraelectric phase transition around 515 K. The polarization hysteresis loops observed at room temperature were attributed to its ferroelectric behavior. Saturated magnetization hysteresis loop with remanent magnetization of 1.54 emu/cm3 was obtained at room temperature. Ferromagnetic ordering in thin films was found to sustain in the entire temperature range from 5 to 395 K, as revealed from the constant behavior of the dM/dT curve with temperature. The mixed oxidation states of palladium (Pd2+/Pd4+) dispersed in the polar Pb(Zr0.20Ti0.80)O3 matrix were revealed from our high resolution x-ray photoelectron spectroscopic studies and is ascribed to the origin of ferromagnetic ordering in the film. These findings suggest that PZTPd thin films are multiferroic (ferroelectric–ferromagnetic) at room temperature.