Showing papers on "Ferroelectric ceramics published in 2008"
TL;DR: In this article, the depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature Tm of the maximum dielectric constant were determined from the temperature dependence of the dielectrics and piezoelectric properties.
Abstract: (1-x)(Bi0.5Na0.5)TiO3–xSrTiO3 (abbreviated as BNST100x) was prepared by a conventional ceramic fabrication process. The depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature Tm of the maximum dielectric constant were determined from the temperature dependence of the dielectric and piezoelectric properties. It is revealed that BNST100x forms a morphotropic phase boundary of rhombohedral ferroelectric and pseudocubic (tetragonal) paraelectric at x=0.26–0.28 for BNST100x, and a very large strain and normalized strain d33* of 0.29% and 488pm∕V, respectively, were obtained at x=0.28. In addition, it was clarified that the intermediate phase between TR-T (⩾Td) and Tm shows relaxor behavior.
336 citations
TL;DR: In this article, the relationship between phase diagrams and the electrical properties of (Bi1/2Na 1/2)TiO3 (BNT)-based solid solutions was demonstrated.
Abstract: In this study, we demonstrated the relationship between the phase diagrams and the electrical properties of (Bi1/2Na1/2)TiO3 (BNT)-based solid solutions. In this study, (1−x)(Bi1/2Na1/2)TiO3–xNaNbO3 and (1−x)(Bi1/2Na1/2)TiO3–xKNbO3 (abbreviated to BNT-NN100x and BNT-KN100x) ceramics were prepared by a conventional ceramic fabrication process, and (1−x)(Bi1/2Na1/2)TiO3–x(Bi1/2K1/2)TiO3 (abbreviated to BNKT100x) ceramic was prepared for comparison. We revealed the phase transition temperatures, such as the depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature Tm of the maximum dielectric constant, from the temperature dependence of dielectric properties using poled and unpoled specimens. As a result, it was shown that the BNT-based solid solutions form three types of phase diagrams. In addition, we clarified the relationship between the phase diagrams and the electrical properties of BNT-NN100x, BNT-KN100x, and BNKT100x. The piezoelectric properties we...
327 citations
TL;DR: In this article, the room temperature ferroelectric and piezoelectric properties of lead-free ceramics were studied based on the measured properties, and two groups were categorized into two groups: group I and group II compositions displaying mixed ferro-electric and antiferroelectric properties at room temperature.
Abstract: Lead-free piezoelectric ceramics, 1� xyBi 0.5 Na 0.5 TiO 3 -xBaTiO 3 -yK 0.5 Na 0.5 NbO 3 0.05x 0.07 and 0.01y 0.03, have been synthesized by a conventional solid state sintering method. The room temperature ferroelectric and piezoelectric properties of these ceramics were studied. Based on the measured properties, the ceramics were categorized into two groups: group I compositions having dominant ferroelectric order and group II compositions displaying mixed ferroelectric and antiferroelectric properties at room temperature. A composition from group II near the boundary between these two groups exhibited a strain as large as 0.45% at an electric field of 8k V/ mm. Polarization in this composition was not stable in that the piezoelectric coefficient d33 at zero electric field was only about 30 pm/ V. The converse piezoelectric response becomes weaker when the composition deviated from the boundary between the groups toward either the ferroelectric or antiferroelectric compositions. These results were rationalized based on a field induced antiferroelectric-ferroelectric phase transition. © 2008 American Institute of Physics. DOI: 10.1063/1.2838472
306 citations
TL;DR: Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric and piezoelectric properties.
Abstract: Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskites. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application. The used method has a significant influence on the structure and properties of barium titanate materials. In this review paper, Part I contains a study of the BaTiO3 structure and frequently used synthesis methods.
291 citations
TL;DR: In this article, the authors present an overview of the recent progress in the synthesis of ferroelectric ceramic powders using various high-energy milling techniques, including direct synthesis of nano-sized powders with better sinterability.
289 citations
TL;DR: In this article, a series of structure transformations depend upon the doping level of Bi1−xLaxFeO3 ceramics with x=0, 0.8La0.2 and Bi0.7La 0.3 have been synthesized by solid state reaction starting from metal oxides.
Abstract: Bi1−xLaxFeO3 ceramics with x=0, 0.1, 0.2, and 0.3 have been synthesized by solid state reaction, starting from metal oxides. A series of structure transformations is found to depend upon the doping level. Below 10% La doping, Bi1−xLaxFeO3 maintains the rhombohedral structure of BiFeO3. However, for Bi0.8La0.2FeO3 and Bi0.7La0.3FeO3, the structures change to the orthorhombic and tetragonal, respectively. La doping significantly reduces electric leakage and leads to successful observation of electrical polarization hysteresis loops. Doping with La also enhances the ferromagnetic moment, due to the broken cycloid spin structure caused by the changes in the crystalline structure.
258 citations
TL;DR: In this article, the temperature dependence of the dielectric and ferroelectric properties of lead-free piezoceramics of the composition (1−x−y)Bi0.5Na 0.5NbO3 was investigated.
Abstract: The temperature dependence of the dielectric and ferroelectric properties of lead-free piezoceramics of the composition (1−x−y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 (0.05⩽x⩽0.07, 0.01⩽y⩽0.03) was investigated. Measurements of the polarization and strain hystereses indicate a transition to predominantly antiferroelectric order when heating from room temperature to 150°C, while for 150
225 citations
TL;DR: In this paper, the depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature of the maximum dielectric constant Tm were determined from the temperature dependences of the dielectrics and piezoelectric properties.
Abstract: (1−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2Li1∕2)TiO3 and (1−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3 (abbreviated as BNLT100x and BNKT100x, respectively) ceramics were prepared by the conventional ceramic fabrication process In this study, the depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature of the maximum dielectric constant Tm were determined from the temperature dependences of the dielectric and piezoelectric properties The results showed that Td of BNLT100x and BNKT100x increased to 199 and 209°C, respectively, at the rhombohedral composition In addition, we revealed that Td is related to the magnitude of the rhombohedrality 90-α and the tetragonality c∕a We studied the piezoelectric properties in detail, and the relationship between Td and piezoelectric properties was clarified Moreover, we discussed the ferroelectricity of the middle phases of Td−TR-T and TR-T−Tm
184 citations
TL;DR: The phase angle of the third harmonic of polarization response (δ3) is very sensitive to the aging state of hard, Fe-doped lead zirconate titanate [Pb(Zr,Ti)O3 or PZT] ceramics and may provide rich information on processes responsible for aging in hard ferroelectrics.
Abstract: It is shown that the phase angle of the third harmonic of polarization response (δ3) is very sensitive to the aging state of hard, Fe-doped lead zirconate titanate [Pb(Zr,Ti)O3 or PZT] ceramics and may thus provide rich information on processes responsible for aging in hard ferroelectrics. When hard PZT ceramics experience hardening (aged state)-softening (deaged state) transition, δ3 changes by about 90° at subswitching fields and by about 180° at switching conditions. Evolution of δ3 with time, temperature and electric field amplitude during deaging suggests that at least two mechanisms of charge migration, one short-range and one long-range, may participate in the deaging process.
142 citations
TL;DR: In this article, two-dimensional multilayer and three-dimensional random powders were designed for high frequency applications using Spark Plasminer Sintering (SPS) to obtain highly densified ferroelectric-dielectric ceramic composites.
Abstract: Spark plasma sintering (SPS) is an efficient tool to obtain highly densified ferroelectric-dielectric ceramic composites with clean interfaces and tunable properties. Dielectric MgO and ferroelectric Ba0.6Sr0.4TiO3 (BST) were combined in two-dimensional multilayer and three-dimensional random powders design. Their unmodified BST Curie temperature proves the suppression of interdiffusion while dielectric losses are below 0.5% and the tunability is 40% at room temperature. The composites and pure BST with similar densities (>95%) were obtained, owing reliable comparison of their dielectric properties. Such SPS ceramics can be used as experimental input for simulation and are potential candidates for high frequency applications.
135 citations
TL;DR: In this article, the electrocaloric characteristics of 0.87PMN-0.13PT ceramics were determined by direct measurements and a strong transition was found at about 18°C, which is the same as the depolarization temperature Td.
Abstract: Only little data have been published on direct electrocaloric measurement of Pb(Mg1∕3Nb2∕3)O3–PbTiO3 (PMN-PT) ceramics. In this paper, the electrocaloric characteristics of 0.87PMN-0.13PT ceramic were determined by direct measurements. A strong transition in the electrocaloric effect was found at about 18°C, which is the same as the depolarization temperature Td. The maximum electrocaloric temperature rise was ΔT=0.558°C at TECm=70°C and E=2400kV∕m, well above the transition at Td=18°C. The existence of two maximums could be an indication of several mechanisms being responsible for the electrocaloric effect.
TL;DR: In this paper, a solid-state sintering process was used to prepare TiO2-rich CaCu3Ti4O12 (CCTO) ceramics by a solid state sinterding process and observed large nonlinear electrical and high dielectric behaviors.
Abstract: We prepared TiO2-rich CaCu3Ti4O12 (CCTO) ceramics by a solid-state sintering process and observed large nonlinear electrical and high dielectric behaviors. Microstructure and phase composition analyses show that CCTO grain-amorphous/TiO2 nanograin boundary-CCTO grain junction structures exist in these TiO2-rich CCTO ceramics, which leads to the nonlinear electrical and high dielectric properties. The temperature dependence of impedance spectroscopy and relationships between electrical current density versus applied electrical field indicate that the activation energy of the grain boundary for the TiO2-rich CCTO ceramics is almost the same as the potential barrier height and both of them are weakly independent of the doped concentration of TiO2, which supports the internal barrier layer capacitor model of Schottky barriers at the grain boundaries between semiconducting CCTO grains.
TL;DR: In this paper, the effect of the grain size on the poling process and dielectric and piezoelectric properties of modified donor doped ferroelectric Pb(Zr,Ti)O3 ceramics having different grain sizes has been studied.
Abstract: The properties of piezoelectric ceramic materials are strongly dependent on the degree of polarization as set by the poling process. As the polarization depends on the domain wall mobility, which in turn depends on the domain size and grain size, the current study focuses on the effect of the grain size on the poling process and dielectric and piezoelectric properties. Polarization and pyroelectric, dielectric and piezoelectric properties of modified donor doped ferroelectric Pb(Zr,Ti)O3 ceramics having different grain sizes have been studied. The dielectric and piezoelectric parameters greatly improved at room temperature with increasing grain size. The Curie temperature (160 °C) is found to shift slightly (by about 7 °C) towards higher temperatures as the grain size increases (2–10 μm). It is concluded that, an optimum choice of a combination of poling field and grain size leads to optimum physical properties. A limited dependence of the dielectric properties on the grain size in non-poled state exists. The dominant contribution to the dielectric properties in the different conditions of the material is discussed.
01 Jan 2008
TL;DR: In this paper, the symmetry aspects of the piezoelectric effect in various materials (single crystals, ceramics, and thin films) are briefly overviewed, and the third-rank tensor of PDE coefficients defined in the crystallographic reference frame is discussed.
Abstract: In this chapter, the symmetry aspects of the piezoelectric effect in various materials (single crystals, ceramics, and thin films) are briefly overviewed. First, the third-rank tensor of piezoelectric coefficients defined in the crystallographic reference frame is discussed. On this basis, the orientation dependence of the longitudinal piezoelectric response in ferroelectric single crystals is described. This dependence is especially important for relaxor single crystals, where a giant piezoelectric effect is observed. Then, the effective piezoelectric constants of polydomain crystals, ceramics, and thin films and their dependence on crystal symmetry are discussed. The domainwall contribution to the piezoelectric properties of ferroelectric ceramics and thin films is also described. Finally, the crystallographic principles of piezomagnetic, magnetoelectric, and multiferroic materials are presented.
01 Jan 2008
TL;DR: Barium titanate is a member of a large family of compounds with the general formula ABO3 which is called perovskite as discussed by the authors, and can be prepared using different methods.
Abstract: Barium titanate is the first ferroelectric ceramics and a good candidate for a variety of applications due to its excellent dielectric, ferroelectric and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 which is called perovskite. Barium titanate can be prepared using different methods. The synthesis method depends on the desired characteristics for the end application and the method used has a significant influence on the structure and properties of barium titanate materials. In this review paper, in Part II the properties of obtained materials and their application are presented.
TL;DR: In this article, the temperature dependence of the dielectric permittivity of perovskite Ba(ZrxTi1−x)O3 solid solutions, PbMg1/3Nb2/3O3 relaxor, and BaTiO3 ferroelectric ceramics was measured.
Abstract: The temperature dependence of the dielectric permittivity of perovskite Ba(ZrxTi1−x)O3 solid solutions, PbMg1/3Nb2/3O3 relaxor, and BaTiO3 ferroelectric ceramics was measured. It is found that a Lorentz-type law can be used to describe the dielectric permittivity of either the normal ferroelectrics with or without diffuse phase transitions (DPT) or the typical ferroelectric relaxors. The ferroelectric DPT can be well described by just one fitting process using the Lorentz-type law, while the relaxor ferroelectric transition needs two independent fitting processes. The Lorentz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric phase transition. Above the transition temperature, the dielectric curves of all the studied materials can be well described by a Lorentz-type law.
TL;DR: In this article, the authors analyzed the nonlinear response of pure and doped Pb(Zr1−xTix)O3 ceramics, with different compositions, to evaluate the domain wall motion in these materials.
Abstract: Nonlinear response of pure and doped Pb(Zr1−xTix)O3 ceramics, with different compositions, has been analyzed in order to evaluate the domain wall motion in these materials. The study of dielectric and converse piezoelectric response shows a clear dependence of the domain wall mobility on the ferroelectric phase. Large lattice distortion in tetragonal samples produces a low mobility of the ferroelectric-ferroelastic domain walls. The influence of the type of defects on the nonlinear response has been explored. The results show that the relative increase of the domain walls mobility in donor-doped materials is greater than the decrease in acceptor-doped materials due to the pinning produced by complex defects. Rayleigh law has been used to evaluate the irreversible contribution of the domain walls movement to the nonlinear dielectric response. The analysis reveals that in presence of oxygen vacancies, the dielectric response cannot be attributed exclusively to the contribution of the irreversible domain wal...
TL;DR: In this article, the photoluminescence spectra of (Ba077Ca023)TiO3:Pr3+ were sensitive to both polarization and phase transitions of the ferroelectric ceramics.
Abstract: We reported in this study that the photoluminescence (PL) spectra of (Ba077Ca023)TiO3:Pr3+ were sensitive to both polarization and phase transitions of the ferroelectric ceramics Comparing with the unpoled sample, all the red emissions under different temperatures of 50to300K increase about 30% for the poled 01mol% Pr3+-doped ceramic Obvious peaks around 100K for the red and blue emission intensities of Pr3+ ions were found when the ceramic passed through the orthorhombic-tetragonal phase transition, and a step decrease in the red emission intensity occurs around the tetragonal-cubic transition Both polarization and phase transition effects on the Pr3+ PL were ascribed to local environmental changes of Pr3+ ions in the (Ba077Ca023)TiO3 ceramic
TL;DR: In this paper, the effect of A-site substitution on the piezoelectric coefficient, high-temperature dc resistivity, and thermal depoling behavior of Aurivillius phase CaBi2Nb2O9 ferroelectric ceramics was investigated.
Abstract: The effect of A-site substitution on the piezoelectric coefficient, high-temperature dc resistivity, and thermal depoling behavior of Aurivillius phase CaBi2Nb2O9 ferroelectric ceramics was investigated. Ceramics with the general formula of Ca1−xMxBi2Nb2O9, where M=Na, (Na,Ce), (Na,La), and La, were prepared by conventional solid-state sintering. All the ceramics were single-phase ferroelectrics with high Curie points (∼900°C). The doped ceramics, Ca0.9Na0.1Bi2Nb2O9, Ca0.9(NaLa)0.1Bi2Nb2O9, Ca0.95La0.05Bi2Nb2O9, and Ca0.9La0.1Bi2Nb2O9, had improved resistance to thermal depoling compared with Ca2Bi2Nb2O9 and were stable up to 800°C. The donor dopants increased the dc electrical resistivity, while the acceptor dopants decreased it. The donor-doped Ca0.95La0.05Bi2Nb2O9 had a higher piezoelectric constant (d33=12.8 pC/N) compared with CaBi2Nb2O9 (d33=5.8 pC/N), and its electrical resistivity was higher than 106Ω·cm at 600°C. These properties suggest that doped CaBi2Nb2O9 ceramics might be good candidates for high-temperature piezoelectric applications.
TL;DR: In this article, complex impedance analysis of polycrystalline tungsten-bronze structured Ba5SmTi3Nb7O30 prepared by a solid-state reaction method was performed.
TL;DR: In this article, the effects of K content on the dielectric, piezoelectric and ferroelectric properties of 0.95KxNN−0.05LS ceramics were studied.
Abstract: The effects of K content on the dielectric, piezoelectric, and ferroelectric properties of 0.95(KxNa1−x)NbO3−0.05LiSbO3 (0.95KxNN−0.05LS) (x=0.25–0.75) lead-free piezoelectric ceramics prepared by conventional solid-state sintering were studied. The experimental results show that the dielectric, piezoelectric, and ferroelectric properties strongly depend on K content in the 0.95KxNN−0.05LS ceramics. The 0.95KxNN−0.05LS (x=0.40) ceramics exhibit enhanced electrical properties (d33≈280 pC/N; kp≈49.4%; Tc∼364 °C; To-t=25 °C; er≈1463; tan δ≈2.3%; Pr∼30.8 μC/cm2; Ec∼14.0 kV/cm). The enhanced electrical properties of 0.95KxNN−0.05LS (x=0.40) ceramics are attributed to the polymorphic phase transition near room temperature. These results show that 0.95KxNN−0.05LS (x=0.40) ceramic is a promising lead-free piezoelectric material.
TL;DR: In this paper, the structural and electrical effects that enhance the domain mobility are investigated, as reflected by hysteresis loops, leading to easier poling and eventually to better piezoelectric properties.
Abstract: Poling of hard ferroelectric ceramics is not an easy process. Pinning of domain walls due to defects prevents the material to be switched by moderate conditions of poling. In this paper, we try to explore a way to facilitate the poling process by defeating the counteracting defects in lead zirconate titanate (PZT). We focus on the structural and electrical effects that enhance the domain mobility, as reflected by hysteresis loops. Increased mobility leads to depinched hysteresis loops and consequently to easier poling and eventually to better piezoelectric properties. Different poling conditions were applied to ceramic samples sintered at different temperatures before and after hysteresis depinching. Dielectric parameters were measured after each poling state. The results showed that the hard ceramic can be efficiently polarized only after domain depinning, which can be done by various methods.
TL;DR: In this article, the key role of ceramic process science in the exploitation of ferroelectric ceramics over the last 50 years is reviewed, focusing on the development of the most important commercial examples, primarily barium titanate-based capacitors and piezoelectric PZT.
Abstract: The key role of ceramic process science in the exploitation of ferroelectric ceramics over the last 50 years is reviewed. Focussing on the development of the most important commercial examples, primarily barium titanate-based capacitors and piezoelectric PZT, the importance of phase equilibria, sintering, defect chemistry and microstructure control are examined. The part played by process science in the increasing significance of ferroelectric thin films and the resurgence of grain-oriented materials is also discussed. The case of multiferroic and magnetoelectric materials is presented as a new challenge poses to ceramic scientists.
TL;DR: In this paper, a powder-in-sol precursor hybrid processing route was proposed to synthesize dense, homogenous, and fine-grained Ni0.5Zn 0.5Fe2O4−Pb(Zr0.53Ti0.47)O3 (NZFO-PZT) composites and report their ferromagnetic-ferroelectric characteristics.
Abstract: We present a powder-in-sol precursor hybrid processing route to synthesize dense, homogenous, and fine-grained Ni0.5Zn0.5Fe2O4–Pb(Zr0.53Ti0.47)O3 (NZFO–PZT) multiferroic ceramic composites and report their ferromagnetic-ferroelectric characteristics. Nanosized NZFO ferromagnetic powders are dispersed into PZT ferroelectric sol-gel precursor and uniformly distributed slurry is prepared by ball-milling mixing of the powder-precursor suspension prior to be sintered at low temperatures to form the composites. The composites show simultaneous effects of ferromagnetism and ferroelectricity at room temperature with excellent magnetic and dielectric properties for frequencies over 10 MHz. The coexistence of inductive and capacitive natures in the composites favors size reduction and design simplification in many passive electronic devices such as integrated filters and microwave absorbers.
TL;DR: In this article, a piezoresponse force microscopy was performed on polished surfaces in both vertical and lateral regimes and depends on the grain orientation varying in both sign (polarization direction) and amplitude.
Abstract: SrTiO3 ceramics are investigated by piezoresponse force microscopy. Piezoelectric contrast is observed on polished surfaces in both vertical and lateral regimes and depends on the grain orientation varying in both sign (polarization direction) and amplitude. The observed contrast is attested to the surface piezoelectricity due to the flexoelectric effect (strain gradient-induced polarization) caused by the surface relaxation. The estimated flexoelectric coefficient is approximately one order of magnitude smaller as compared to that recently measured in SrTiO3 single crystals. The observed enhancement of piezoresponse signal at the grain boundaries is explained by the dipole moments associated with inhomogeneous distribution of oxygen vacancies.
TL;DR: In this paper, it was observed that almost no chemical reaction occurs between the ferrite and the ferroelectric materials used to form the diphase composite systems, which showed marked improvement as high as 57% and confirmed the coupling of the electrical dipoles with the magnetic field applied.
Abstract: Multiferroic ceramics with the general formula (x)MgFe2O4–(1−x)BaTiO3 (x=04, 05, and 06) were synthesized by solid-state sintering process From the x-ray diffraction analysis, it was observed that almost no chemical reaction occurs between the ferrite and the ferroelectric materials used to form the diphase composite systems No impure phase was observed in all the sintered composite systems Leakage current density, ferroelectric properties and dielectric properties were found to improve with the addition of the ferroelectric phase For the composite with the least amount of ferrite, the values of remnant polarization (2Pr) before and after dc magnetic poling at 7kOe for 1h were found to be 135 and 212μC∕cm2, respectively This showed marked improvement as high as 57% and confirmed the coupling of the electrical dipoles with the magnetic field applied All the studied composite systems proved to be multiferroic in nature The highest magnetoelectric coupling coefficient of 502mV∕cmOe was measured
TL;DR: In this article, the electrical properties of tungsten bronze ferroelectric ceramics of Pb 0.77 K 0.115 Nb 2 O 6 (Sm:PKN) over a wide frequency (45-Hz to 5-MHz) and temperature (35-600°C) range were investigated.
TL;DR: In this article, the effects of LN substitution through the dielectric and ferroelectric properties of Na0.5K 0.5NbO3 (NKN) and 0.95NKN-0.05LN thin film (350nm) were investigated.
Abstract: We have fabricated environmental friendly lead-free ferroelectric Na0.5K0.5NbO3 (NKN) and 0.95Na0.5K0.5NbO3–0.05LiNbO3 (0.95NKN-0.05LN) thin films by chemical solution deposition using metal-organic compounds, and studied the effects of LN substitution through the dielectric and ferroelectric properties. The small amount of LN substitution for NKN thin film led to a marked improvement in leakage current properties at the high electric field region. Furthermore, the 0.95NKN-0.05LN thin film (350nm) displayed clear ferroelectricity with well saturated P-E hysteresis loop with 2Pr and 2Ec values of 19.5μC∕cm2 and 91kV∕cm, respectively. The 0.95NKN-0.05LN films will be interesting for applications in lead-free ferroelectric and piezoelectric devices.
TL;DR: In this article, the dielectric relaxations of charge-ordered Ln1.5Sr0.5NiO4 (Ln=La and Nd) ceramics were investigated over a broad temperature range.
Abstract: Dielectric relaxations of charge-ordered Ln1.5Sr0.5NiO4 (Ln=La and Nd) ceramics were investigated over a broad temperature range. The giant dielectric constant (over 70 000) with a low dielectric loss of ∼0.1 was determined at high frequencies (up to 5 MHz) over a broad temperature range. There are two dielectric relaxations in the vicinity of charge ordering temperatures. The thermal activated small polaronic hopping between two charge ordering temperatures should contribute to the giant dielectric response in the present ceramics. Compared to other giant dielectric constant materials, the present materials have the notable advantage for high frequency applications.
TL;DR: In this article, the authors reported the ferroelectric properties and piezoresponse of the PLD-produced BNKLT thin films, which exhibited a well-defined polarization hysteresis loop with a remnant polarization Pr of 13.9μC∕cm2 and a coercive field Ec of 10.2MV∕m.
Abstract: Polycrystalline lead-free piezoelectric [Bi0.5(Na0.7K0.2Li0.1)0.5]TiO3 (BNKLT) thin films were grown on Pt∕Ti∕SiO2∕Si substrates using pulsed laser deposition (PLD). In this letter, we report the ferroelectric properties and piezoresponse of the PLD-produced BNKLT thin films. X-ray diffraction characterization revealed a good crystallinity and a pure perovskite structure in the films. The films exhibited a well-defined polarization hysteresis loop with a remnant polarization Pr of 13.9μC∕cm2 and a coercive field Ec of 10.2MV∕m. The domain structure and its thermal-driven evolution from the ferroelectric to nonferroelectric phase were observed by piezoresponse force microscopy. The results were consistent with the phase transition profile of BNKLT bulk ceramics. Typical butterfly-shaped piezoresponse loop was obtained and the effective piezoelectric coefficient d33,f of the BNKLT thin films was about 64pm∕V.