Dielectric and pyroelectric properties of (1 − x)PST-xPZT ferroelectric ceramics

Pb(Sc_1/2Ta_1/2)O₃ (PST) ceramics were investigated greatly in the world for their unique pyroelectric, ferroelectric and dielectric properties and comprehensive applications on uncooled focal plane arrays, infrared detectors and other electronic devices. However, the PST ceramics doped with other perovskite ferroelectrics showed more excellent electrical and electronic properties. In this paper, (1???x)PST-xPZT(PSTZT) ferroelectric ceramics were prepared by conventional solid state process. The experiment results demonstrated that the PSTZT ceramics had pure perovskite phase. The temperature dependence of permittivity of PSTZT ceramics was investigated in detail, which indicated that PSTZT was not a complete diffusive phase transition ferroelectric ceramics. At room temperature, the pyroelectric coefficient of PSTZT (x?=?0.1) ceramics was about 15*10^?8C/(cm² K).     

Processing and properties of nanocrystalline Pb(Sc0.5Ta0.5)O3, Pb(Sc0.5nb0.5)O3 and Pb(Mg1/3Nb2/3)O3 films produced by RF-sputtering from ceramic targets

Abstract

Nanocrystalline thin films of different relaxor materials, namely Pb(Sc_0.5Ta_0.5)O₃ (PST), Pb(Sc_0.5Nb_0.5)O₃(PSN), Pb(Mg_1/3Nb_2/3)O₃(PMN) have been produced by RF-sputtering to investigate whether it will affect their dielectric properties if their grain size is reduced to the dimensions known from their nanodomains. The XRD shows that the amorphous film crystallizes in pyrochlore structure at lower temperatures and short times. Annealing at higher temperatures and far longer time intervals leads to an increasing amount of perovskite phase with a grain size in the nanometer range. These results including dielectric measurements will be presented and discussed.     

Multiferroic ceramics Pb(Fe1/2Nb1/2)O3 doped by Li

We present the results of obtaining and investigating multiferroic ceramics Pb(Fe_1/2Nb_1/2)O₃ (PFN) and PFN doped by various amounts of Li (PFN:Li). Ceramics have been obtained from oxides by two-step synthesis. For obtained samples the X-ray diffraction patterns, microstructure, DC electric conductivity, the temperature dependencies of dielectric permittivity and dielectric losses, electromechanical properties and hysteresis loops have been investigated. Obtained results have shown that the introduction of Li decreases electric conductivity and improves dielectric and electromechanical parameters important for applications.     

Dielectric and relaxor ferroelectric properties of Ba-doped Pb(Zr,Ti)O3 ceramics

(Pb,Ba)(Zr,Ti)O₃ is a relaxor ferroelectric material. Dielectric and ferroelectric properties of (Pb_1-x Ba _x )(Zr_0.70Ti_0.30)O₃ ceramics have been investigated for compositions varying in the range of 0.20?≤?x?≤?0.30. Reagent grade PbO, ZrO₂, TiO₂ and BaCO₃ raw powders were used, ceramics were fabricated by convenient solid state reaction. The experimental results show that the substitution of Ba for Pb can enhance the ferroelectric relaxor characteristics. With the Ba content increasing, the electric hysteresis was narrowed and the polarization was reduced. Meanwhile the temperature T _m that corresponding to the maximal dielectric constant was decreased. It has also been found that the hydrostatic pressure may cause the phase transition more diffuse and move T _m to higher temperature.     

Relaxor behavior of piezoelectric Pb(Yb1/2Nb1/2)O3-PbTiO3 ceramics sintered at low temperature

A (100-x)Pb(Yb_1/2Nb_1/2)O₃-xPbTiO₃ [PYN-PTx] solid solution system with 49.0????×????51.0 was prepared using a conventional ceramics process and sintered at low temperature. When excess PbO was added into the PYN-PTx system, all samples were sintered at temperatures as low as 800°C with good dielectric and piezoelectric properties. It is suggested that a liquid phase with excess PbO was formed during the sintering and improved the densification of PYN-PTx ceramics at low temperatures. For the PYN-PTx binary system, it was found that the temperature dependence of the relative permittivity follows a Curie?CWeiss Law above the deviation temperature (T_D) at high temperatures. Good piezoelectric properties of d ₃₃ ?=?510 pC/N, ?? _r ?=?2800 at RT, k _p?=?0.57, and k _t?=?0.42 with T_c?=?373°C were obtained for PYN-PT49.5 ceramics sintered at 800°C for 8 h.     

Enhanced piezoelectric properties of 0.55Pb(Ni1/3Nb2/3)O3-0.135PbZrO3- 0.315PbTiO3 ternary ceramics by optimizing sintering temperature

0.55Pb(Ni_1/3Nb_2/3)O₃-0.135PbZrO₃-0.315PbTiO₃ (PNN-PZ-PT) ternary piezoelectric ceramics with excess 1.0 wt.% PbO were synthesized by the conventional solid-state reaction method at 1175–1300 °C for 2 h, respectively. The influence of sintering temperature (T _s) on microstructure, piezoelectric, dielectric, and ferroelectric properties were systematically investigated. The results of XRD and Raman scattering spectra demonstrated that a typical perovskite structure with mainly rhombohedral symmetry near the MPB region were obtained for all the samples. The tetragonal phase content was increased slightly with the increase of sintering temperature. In addition, with increasing T _s the average grain size increases while the density decreases were also found. The results of electrical measurements confirmed that piezoelectric constant, dielectric constant, remnant polarization were firstly increased and then decreased with the increase of sintering temperature. The optimum and remarkable enhanced electrical properties of d ₃₃?=?1070 pC/N, k _p?=?0.69, ε _r?=?8710, tanδ?=?0.026, P _r?=?24.08 μC/cm², and E _c?=?3.2 kV/cm were obtained for the sample sintered at 1250 °C for 2 h. Meanwhile, the sample exhibits a typical relaxor ferroelectric behavior with the maximum dielectric constant ε _m =24541 at Curie temperature T _c?=?113.3 °C at 1 kHz.     

Substituent Effects in 0.65Pb(Mg1/3Nb2/3O30.35PbTiO3 Piezoelectric Ceramics

Pb(Mg_1/3Nb_2/3O₃–-PbTiO₃ (PMN-PT) ceramics with base compositions close to the morphotropic phase boundary are potential materials for many applications such as transducers and actuators due to their high dielectric constants and electromechanical coupling factors. However, their dielectrical and mechanical losses are too high for high-power applications. In this paper, the dielectric and electromechanical properties of piezoelectric PMN-PT ceramics were investigated in specimens containing various A-site and B-site substituents with the goal of developing lower loss materials for wider applications. Emphasis was placed on various transition metal cation substituents of both lower and higher valences. Mn substituent was found to be the most promising substituent investigated for developing high power low loss piezoelectric PMN-PT ceramics.     

Microstructures and Piezoelectric Properties of Microwave-Sintered Pb(Mn1/3Nb2/3)0.1Zr0.52Ti0.38O3 Ceramics

In this work, we study the microstructural modifications and the electrical properties of Pb(Mn_1/3Nb_2/3)_0.1Zr_0.52Ti_0.38O₃ + 1.5 wt% PbO (PMNZT) ceramics processed using microwave sintering (MS) and conventional sintering (CS) techniques. Dielectric and piezoelectric properties were evaluated via an impedance/gain phase analyzer and the corresponding microstructures were examined using transmission electron microscopy (TEM). The experimental results imply that smaller grain size and less loss of PbO obtained for specimens using MS process. The MS specimens (1200°C-15 min) show the remanent polarization (P_r) of 24.1 μC/cm², coercive field (E_c) of 15.2 kV/cm, dielectric constants (?_r) of 432 and electromechanical coupling coefficient (k_p) of 0.47, which are superior to CS specimens (1200°C-2 h) with P_r = 19.5 μC/cm², E_c = 16.1 kV/cm, ?_r = 395 and k_p = 0.45. The results revealed that the MS process shows capability of fabrication of good quality PMNZT ceramics with advantages of lowing process temperature and shorten process time. TEM investigations of MS specimens show that smaller grain size and simpler domain arrangements exist inside the specimens. From the energy aspect, the domain structure in piezoelectric ceramics below the temperature of a ferroelectric structural phase transformation is a result of energy minimization. Homogeneous elastic strain energy is reduced at the expense of domain boundary energy during the phase transformation. Density of domain boundaries, 71° (109°) domains in particular, depends on and increases with the grain size. Base on the above argument, therefore, CS specimens exhibit more complicated domain arrangements because they possess larger grain size than MS specimens do. The microstructural investigations suggest that the electrical property difference is intimately related to different sintering methods since the complicated domain arrangements could hinder domain moving and deteriorate electrical performance. In addition, the microstructural characteristics in both MS and CS specimens will be discussed further in the context.     

Structure dependence of the ferroelectric properties of Bi3.25Ln0.75Ti3O12 (Ln=La, Nd, Sm, Dy) ceramics

We have fabricated rare-earth ion substituted bismuth titanate (BIT) ceramics, Bi_3.25Ln_0.75Ti₃O₁₂ (BLnT; Ln=La, Nd, Sm, Dy), using the conventional solid-state reaction method and have investigated the changes in the structural distortion and electrical properties, which resulted from the substitution of the rare-earth ions in BIT ceramics. As the ionic radius of the rare-earth ion substituted into the BIT decreased, the structural distortion and decreases in the unit cell volume became more pronounced as well as the Curie temperature increased monotonically from 354 °C (BLaT) to 480 °C (BDyT). BNdT ceramics had relatively high remanent polarization value (12.5 μC/cm²) at an applied electric field of 130 kV/cm. The extent of the structural distortion influenced the dielectric and ferroelectric properties of the BLnT ceramics.     

Dielectric properties and morphotropic phase boundaries in the xPb(Zn1/3Nb2/3)O3−(1−x)Pb(Zr0.5Ti0.5O3 pseudo-binary system

Ceramics in the xPb(Zn_1/3Nb_2/3)O₃−(1−x)Pb(Zr_0.5Ti_0.5)O₃ [xPZN–(1−x)PZT] solid solution system are expected to display excellent dielectric, piezoelectric, and ferroelectric properties in compositions close to the morphotropic phase boundary (MPB). The dielectric behavior of ceramics with x = 0.1−0.6 has been characterized in order to identify the MPB compositions in this system. Combined with X-ray diffraction results, ferroelectric hysteresis measurements, and Raman reflectivity analysis, it was consistently shown that an MPB exists between x = 0.2 and x = 0.3 in this binary system. When x ≤ 0.2, the tetragonal phase dominates at ambient temperatures. In the range of x ≥ 0.3, the rhombohedral phase dominates. For this rhombohedral phase, electrical measurements reveal a profound frequency dispersion in the dielectric response when x ≥ 0.6, suggesting a transition from normal ferroelectric to relaxor ferroelectric between 0.5 ≤ x ≤ 0.6. Excellent piezoelectric properties were found in 0.3PZN–0.7PZT, the composition closest to the MPB with a rhombohedral structure. The results are summarized in a PZN–PZT binary phase diagram.     

Structural and dielectric properties of Ba0.80Sr0.20Ti1 − x Sn x O3 ceramics

The Ba_0.80Sr_0.20Ti_1???x Sn _x O₃ (BSTS) ceramics were prepared by conventional ceramic method. The crystalline structure and morphology were studied by X-ray diffraction and scanning electron microscopy, respectively. The dielectric constant and loss as a function of temperature and external bias electric field were investigated. Experimental results show that with the increasing of sintering temperature, the peak permittivity increases dramatically and tanδ increases at ferroelectric state while does not change apparently at paraelectric state. With the increasing of the Sn⁴⁺ concentration in the BSTS structure, the Curie temperature decreases.     

Composition dependent electrocaloric behavior of (SrxBa1-x)Nb2O6 ceramics

This article presents electrocaloric effect in (Sr_xBa_1-x)Nb₂O₆ ceramics (where x = 0.25, 0.50 and 0.75) using an indirect approach based on Maxwell's relations. Here, we have calculated various parameters of electrocaloric effect like temperature change (ΔT), entropy change (ΔS) and heat carrying capacity (ΔQ) of material due to the change in polarization under two different electric fields of 30 kV/cm and 20 kV/cm. (Sr_xBa_1-x)Nb₂O₆ ceramics is well known pyroelectric material, where by increasing Sr/Ba ratio the ferroelectric behavior turns towards relaxor behavior. While in terms of electrocaloric effect performance (temperature change ΔT) is increase as the Sr/Ba ratio increases. Additionally, maximum ΔT (0.30 K) was found for (Sr_xBa_1-x)Nb₂O₆ ceramic having x=0.75 molar concentration under the electric fields of 30 kV/cm.     

Piezoelectric ceramics of (Bi1/2Na1/2)TiO3-PbTiO3-BaTiO3 system

Piezoelectric and ferroelectric properties of bismuth sodium titanate, (Bi_1/2Na_1/2)TiO₃(BNT)-based solid solution, that is, (Bi_1/2Na_1/2)(_1-x)(Pb_a Ba_b)_xTiO₃(a + b = 1) [BNPB(100x-100a/100b)], are studied from the viewpoint of a new group of lead-free or low-lead content piezo-electric ceramics with a rhombohedral(F_a-tetragonal (F_β) morphotropic phase boundary (MPB). It is evident that the MPB seems to be remarkably efficacious in promoting piezoelectric and pyroelectric activities by electrical poling. X-ray diffraction data, dielectric properties and D-E hysteresis loops show that the MPB exist near (Bi_1/2Na_1/2)TiO₃[BNT] at x = 0.13–0.14, 0.08–0.09 and 0.06–0.07 in the case of b = 0, b = 0.5 and b = 1, respectively. BNPB ceramics are superior for piezoelectric ceramics in high-frequency ultrasonic uses, or special piezoelectric actuator materials with a lower free permittivity ε₃₃Tε₀, and a high electromechanical coupling factor k₃₃, along with a high mechanical strength.     

Dielectric, ferroelectric and ferromagnetic properties of 0.8PbFe0.5Ta0.5O3-0.2PbTiO3 ceramics

Lead based complex compounds, 0.8PbFe_0.5− Ta_0.5O₃-0.2PbTiO₃ (0.8PFT-0.2PT) ceramics, were prepared by the solid state reaction method, and the corresponding dielectric, ferroelectric and ferromagnetic properties were investigated. As the PT phase was added to the PFT phase, the Curie temperature of 0.8PFT-0.2PT ceramics increased. The ferroelectric P-E and ferromagnetic M-H hysteresis loops were observed at the same time. The ferroelectric properties depend on the formation of the perovskite 0.8PFT-0.2PT phase; however, the ferromagnetic properties depend on the formation of the pyrochlore Pb₃FeTaO₇ phase.     

Preparation and properties of Pb(Zr, Ti)O3 ferroelectric thin films and compositionally graded thin films on LaNiO3/Si substrates

LaNiO₃ (LNO) thin films were prepared on Si (100) wafer by MOD method. Pb(Zr, Ti)O₃ ferroelectric thin films and their compositionally graded thin films were prepared on LNO/Si (100) substrates by a modified sol–gel method. The composition depth profile of a graded film was determined by using a combination of Auger electron spectroscopy and Ar ion etching. The results confirmed that the processing method produces graded composition change. XRD analysis showed that the graded thin film possessed a composite structure of tetragonal and rhombohedral. The dielectric constant of the graded thin films was higher than that of each thin film unit, but the loss tangent was near to each other at 10 kHz. The temperature characteristics of the dielectric constant of the graded thin films at different frequencies showed three peaks and ferroelectric relaxor feature to some extent. Hysteresis loops showed that graded thin film had higher remanent polarization, smaller coercive field than each thin film unit. The pyroelectric coefficient of the graded thin films increased gradually with temperature, and was higher than that of each thin film unit.     

Ferroelectricity in Aurivillius-Type Structure Ceramics with n = 2 and (SrBi2Nb2O9)0.35(Bi3TiNbO9)0.65 Composition

Aurivillius-type structure compounds are good candidates for their use as high temperature piezoelectrics, due to their high ferro-paraelectric phase transition temperature. However, this characteristic correlates with a high coercive field that makes difficult the poling process, necessary to have piezoelectric activity. The electric properties, specially conductivity, limit the maximum poling field. On the other hand, piezoelectric properties are directly related to the ferroelectric remanent polarization. Thus, the study of both characteristics is towards improving the piezoelectric properties of these materials. In this work, ceramics with nominal composition (SrBi₂Nb₂O₉)_0.35(Bi₃TiNbO₉)_0.65 (T_C∼ 760^∘C), prepared by hot pressing of mechanically activated precursors, have been studied. The electrical properties (permittivity, dielectric loss factor and d.c. conductivity) as a function of frequency and temperature have been measured, up to temperatures higher than the ferro-paraelectric phase transition, and their anisotropy explained in terms of the ceramic texture. Well-saturated ferroelectric hysteresis loops at 250^∘C have been obtained, with values of P_r = 21.4 μ C/cm² and E_c = 70.4 kV/cm.     

Piezoelectric and ferroelectric properties of new Pb9Ce2Ti12O36 and lead-free Ba2NdTi2Nb3O15 ceramics

In this paper, measurements of the nonlinear ferroelectric, piezoelectric and dielectric properties of Pb₉Ce₂Ti₁₂O₃₆ (Pb₉CTO) and Ba₂NdTi₂Nb₃O₁₅ (BNTN) ferroelectric ceramics are presented. Hysteresis P(E) loops were measured as a function of applied electric field, frequency and temperature. The coercive field (E _c) and remnant polarization (P _r) displayed temperature and frequency dependence. Lead-free BNTN ceramics exhibited a coercive field E _c?>?2.4 kV mm^?1 and a piezoelectric coefficient d ₃₃?=?2 pC N^?1. The hysteresis loop was pinched above 110°C and a linear response was observed at 155°C, typical of a paraelectric material. Pb₉CTO was shown to be ferroelectric with coercive field E _c?=?1.2 kV mm^?1 and a d ₃₃?=?65 pC N^?1. The frequency dependences of the impedance of the Pb₉CTO discs were analyzed.     

Depth-dependence of electromechanical properties in a thick 0.7Pb(Mg1/3(Nb0.9Ta0.1)2/3)O3–0.3pbtio3 ceramic disk

A thick ceramic disk of 0.7Pb(Mg_1/3(Nb_0.9Ta_0.1)_2/3)O₃–0.3PbTiO₃ (PMNT–PT) was prepared by columbite precursor method with PbO powder buffer surrounding the disk during the sintering process. The Electromechanical properties and the microstructure of PMNT–PT samples cut from the different depths of the disk are studied. Although the phase purity is homogenous in the whole disk, the middle sample has higher electric field induced strain. Electric field of 14 kV/cm induced strain 0.14% was found. It is believed that the prepared processes, especially the Pb volatilization is responsible for these results.     

Low temperature sintering of screen-printed Pb(ZrTi)O3 thick films

Abstract

There has been increasing interest in ferroelectric lead zirconate titanate (PZT) films for the applications in piezoelectric and pyroelectric devices. Many potential applications require a film thickness of above 10 μm for higher force, better sensitivity and stability. But it is very difficult to fabricate the PZT thick film on the silicon substrate because of the volatility of PbO and the interdiffusion of the Pb and Si through the bottom electrode during the sintering at normal temperatures (such as above 1200°C). We speculated densification and reaction mechanism of the PZT thick films fabricated at relatively low temperature (under 1000°C) without sintering aids. The PZT thick films were screen-printed on Pt / Al₂O₃ substrate using a paste of PbO, ZrO₂ and TiO₂ powder mixture. Highly densified PZT thick films could be fabricated on Pt / Al₂O₃ substrate at 1000°C, and we achieved the density, remanent polarization, coercive field, dielectric permittivity, dissipation factor and breakdown field of 98%, 10 μC/cm² and 20 kV/cm, 540, 0.009 and 15 MV/m, respectively. The results show the possibility of densification of the PZT thick film at relatively low temperature without sintering aids, and the results are promising for the use of PZT thick films in various applications.     

High temperature processing of ferroelectric thin films using interconnect wafer technology

Abstract

There is interest in ferroelectric thin films for uncooled IR detector applications. Currently the processing of these devices takes a fully integrated approach where the thin films are deposited directly onto underlying CMOS readout circuitry, thereby imposing severe limits on the thermal budget available for the crystallisation of the ferroelectric material. This is incommensurate with obtaining the best ferroelectric properties from materials such as lead scandium tantalate (PST) which requires elevated temperature processing to attain the highest merit figures for IR detection. In this paper thin film PST processed within the CMOS survivability envelope will be compared to that processed at temperatures up to 850°C. A novel interconnect wafer technology will be outlined which enables processing to be extended to such temperatures. It will be shown that elevated temperature processing of the PST film can result in dramatic improvement of the materials merit figure for IR detection