Antiferroelectric Lead Zirconate Research Articles

Electron emission from La-doped Pb(Zr,Sn,Ti)O3 anti-ferroelectrics by pulse electric field and the relevant physical mechanism

We investigate the characteristics of emission current waves of antiferroelectric cathode material lanthanum-doped lead zirconate stannate titanate (PLZST) triggered by pulse field, and analyze the relationship of the emission current waveforms with the extraction voltage. The close correlation between the triggering pulse polarity and emission current waveform observed evidences the relevant physical process of electron emission. We speculate that the primary emission may result from local phase transition and field emission in the vicinity of triple junctions, and the plasma formation may enhance the electron emission.

Symmetry of the Antiferroelectric Lead Zirconate

The symmetry of the antiferroelectric phase of PbZrO3 was mainly regarded as C 2v 8 or D 2h 9 in the previous literatures. Both of them belong to the orthorhombic system. It is reinvestigated in this paper by symmetry element analysis based on the projective figures given in the related literatures. We find that the symmetry group of this antiferroelectric (AFE) phase is C 2h 1, and the antiferroelectric crystal PbZrO3 belongs to the monoclinic system. The dielectric tensor measurement was proposed to distinguish the space group C 2h 1 from C 2v 8 and D 2h 9.

Antiferroelectric Lead Zirconate Ceramics with Nanoparticle Alumina Additions

The effects of alumina nanoparticles on the properties of PbZrO3 ceramics were investigated. The samples were prepared by a simple conventional mixed oxide method involving calcination and sintering temperatures of 800 oC and 1200 oC, respectively. Single-phase lead zirconate was observed in X-ray powder diffraction patterns for all the samples. The relationship between the Al2O3 content, the dielectric properties and Knoop hardness were determined. The results indicate that the additive affects Curie temperatures and the shape of the Curie peak, implying a chemical reaction takes place with the matrix during high-temperature processing. Hardness values increase for additions up to 1 vol % Al2O3.

Influence of pulse polarity on electron emission property of antiferroelectric ceramic

The electron emission property of a novel antiferroelectric cathode material lanthanum-doped lead zirconate stannate titanate (PLZST) on the application of positive or negative triggering voltage pulses has been investigated. All experiments were performed in a vacuum of 10−5 Torr and at room temperature. It was discovered that there were two electron emission pulses when low positive triggering voltage was applied to the rear electrode, and three electron emission pulses when high positive triggering voltage was applied. However there were always two electron emission pulses when negative triggering pulses were applied. This phenomenon is proposed to be a result of both field electron emission at triple junctions and electron emission caused by polarization reversal. The experimental observations indicate that domain movement in the vicinity close to the triple junction under application of the triggering voltage pulse may be a primary origin of electron emission from PLZST.

Characteristics of electron emission from La-doped Pb(Zr,Sn,Ti)O 3 antiferroelectric cathode under negative triggering pulse

The electron emission property of a novel antiferroelectric cathode material lanthanum-doped lead zirconate stannate titanate (PLZST) on application of negative triggering voltage pulses has been investigated. It was found that strong electron emission from PLZST could be achieved under lower triggering voltage at room temperature. There were always two electron emission pulses when negative triggering pulses were applied. A large emission current of 690 A was obtained with a negative triggering voltage of 500 V and extraction voltage of 3.5 kV. Strong electrons emission was the co-effect of surface plasma and noncompensated negative charges at the surface of the antiferroelectric. Field-induced local phase transition in the vicinity close to triple junction results in primary electron emission from these areas. These primary emission electrons ignited surface plasma and then leaded to the strong emission.

Electrical properties and leakage current behavior of un-doped and Ti-doped lead zirconate thin films synthesized by sol–gel method

Un-doped and Ti-doped (5, 10 and 15 mol%) antiferroelectric and ferroelectric lead zirconate–PbZrO 3 (PZ) thin films were prepared by sol–gel spin coating method. All PZ films crystallized in the perovskite phase with full [111] pseudocubic orientation with a uniform microstructure. The paraelectric–ferroelectric phase transition temperature was found to shift to lower values and the electrical properties were found to degrade as a result of decreasing film thickness. The leakage current of the un-doped PZ films were dominated by the space-charge-limited current, whereas Poole–Frenkel conduction mechanism was found to be dominant at the Ti-doped films at high electric fields.

Synthesis and structural characterization of the antiferroelectric lead zirconate nanotubes by pulsed laser deposition

For the first time, a pulsed laser ablation deposition (PLD) method has been employed for the synthesis of antiferroelectric lead zirconate, PbZrO3, (PZ) nanotubes within the pores of anodic aluminum oxide (AAO) templates. The structure and morphology of fabricated PZ nanotubes were characterized by number of techniques, including scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM)analysis. After postannealing at 650 °C, the PZ nanotubes exhibited a polycrystalline microstructure, and X-ray diffraction studies revealed that they are of an orthorhombic distorted perovskite crystal structure. TEM analysis confirmed that the obtained PZ nanotubes are composed of nanoparticles in the range of 3–7 nm and the thickness of the wall of the nanotubes is around 10 nm.

Electric fatigue in antiferroelectric ceramics induced by bipolar electric cycling

The fatigue behavior of antiferroelectric lanthanum-doped lead zirconate stannate titanate bulk material induced by bipolar cycling was investigated. Strain and polarization hysteresis loops, acoustic emissions (AEs), and biaxial strength were monitored. The material showed a high resistance to electric fatigue, concerning the losses in maximum strain, switchable polarization, and biaxial strength as well as modifications of AE patterns and microstructure. Fatigue microcracking is weak in the material during cycling. The pinning of antiferroelectric and ferroelectric domains by point defect agglomeration is discussed as the main fatigue mechanism. A diffuse antiferroelectric-ferroelectric phase transition and an asymmetry of the strain hysteresis loop due to the electric cycling are described and explained as a result of the pinning process and offset polarization.

Electric fatigue in antiferroelectric Pb 0.97La 0.02(Zr 0.55Sn 0.33Ti 0.12)O 3 ceramics induced by bipolar cycling

Antiferroelectric lead zirconate titanate stannate (PZST) ceramics are promising materials for high-strain transducers and actuators. The degradation of the strain excited by an ac field remains largely unknown so far for this family of antiferroelectric ceramics. In this study, the bipolar electric fatigue of antiferroelectric Pb 0.97La 0.02(Zr 0.55Sn 0.33Ti 0.12)O 3 ceramics was investigated. Variations in the strain hysteresis loop and damage in the microstructure of the materials due to the electric cycling were monitored. Higher cycling field yielded a stronger fatigue effect. The material showed an increasingly asymmetric suppression of the strain hysteresis loop and diffuse AFE–FE phase transition with increasing cycle number. A damaged microstructure was observed on the polished surfaces of fatigued samples after acid etching. Electrochemical variations, the pinning of domains, randomly or preferentially orientated, due to the cycling are considered as the main fatigue mechanism of the material.

Effects of postdeposition annealing on the dielectric properties of antiferroelectric lanthanum-doped lead zirconate stannate titanate thin films derived from pulsed laser deposition

Lanthanum-doped lead zirconate stannate titanate antiferroelectric thin films were deposited onto Pt-buffered silicon substrates using the pulsed laser deposition method. The deposition temperature was 570°C. The postdeposition annealing process was carried out in an oxygen-flow tube furnace at temperatures ranging from 650 to 800°C for a duration of 30min; its effects were studied through the variations of the microstructure as well as the electrical and dielectric properties. It was found that an appropriate annealing process at temperatures above 700°Ccould substantially improve the dielectric properties. However, annealing beyond 800°C caused the film properties to deteriorate severely. Explanations were given with regard to the microstructure-property relationship.

Role of oxygen pressure during pulsed laser deposition on the electrical and dielectric properties of antiferroelectric lanthanum-doped lead zirconate stannate titanate thin films

Lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films of ∼420 nm with compositions in the antiferroelectric tetragonal region have been prepared on Pt-buffered Si substrates by pulsed laser deposition. Effects of oxygen pressure during deposition were studied, with emphasis placed on the electrical and dielectric properties of the films. The dielectric constant and the maximum polarization increased with the oxygen pressure during deposition, from 75 to 125 mTorr. So did the dielectric strength. This property enhancement with deposition oxygen pressure was believed to be due to the reduction of pyrochlore phase in the films. However, increasing the oxygen pressure beyond 150 mTorr during deposition had led to the increase of surface roughness, which eventually resulted in film cracking. It was also found that increasing the oxygen pressure did not benefit the fatigue performance in any appreciable way.

Effect of Sn doping on the phase transition behaviors of antiferroelectric lead zirconate titanate

The effects of stannate doping on the phase transition behaviors of antiferroelectric lead zirconate titanate were examined. It was shown that addition of Sn causes an increase in the switching electric fields and a decrease in the electric hysteresis. On the other hand, as Sn/Zr ratio increased both antiferroelectric orthorhombic to tetragonal phase and subsequent antiferroelectric to paraelectric phase transition temperatures decreased, and the maximum dielectric peak that related with antiferroelectric to paraelectric transition was diffused.

Dielectric behaviour of antiferroelectric lead zirconate titanateunder strong electric field

The dielectric behaviour of antiferroelectric lead zirconate titanate has been studied by measuring the polarization and capacitance changes with the electric field.The results show that the differential dielectric constant εd calculated from the polarization versus electric field curve exhibits sharp peaks at the electric fields that switch an antiferroelectricsferroelectrics transition,and the maximum value of εd can reach up to 41000. The smallsignal dielectric constant εc measured will decrease rapidly during the phase transition from an antiferroelectric state to a polarized ferroelectric state by increasing the dc bias field, and εc will increase during the ferroelectric state returns to the original antiferroelectric state by reducing dc bias field. It is noticed that the extreme values of the differential dielectric constant εd are electric hysteretic to the extreme of the small signal dielectric constant εc. These phenomena are analyzed by using the electric domain evolution under an electric field.

Study of La-modified antiferroelectric PbZrO 3 thin films

Dielectric and DC electrical properties of antiferroelectric lead zirconate and La-doped lead zirconate thin films deposited using a pulsed excimer-laser ablation technique were studied in detail. Increased La dopant concentration in pure lead zirconate thin films reduced the dielectric maximum and Curie temperature. At 9 mol.% of La in pure lead zirconate, the dielectric transition temperature reduced to room temperature. A gradual change from antiferroelectric to paraelectric through ferroelectric phases was observed with the addition of La to pure lead zirconate. The DC electrical properties of pure lead zirconate and the effect of donor addition on leakage current properties were studied. Correlation between the macroscopic changes observed in the charge transport mechanisms, microscopic defect chemistry and charge-carrier trapping phenomenon was examined in detail.

The effect of neutron irradiation on the curie-weiss temperature of an antiferroelectric lead zirconate film

A physical model describing variations of the Curie-Weiss temperature of an antiferroelectric lead zirconate (PbZrO3) film under neutron irradiation is proposed. According to this model, a relative change in the Curie-Weiss temperature is proportional to the square of the total neutron dose. Theoretical estimates are in good agreement with experimental data.

Ac transport studies of La-modified antiferroelectric lead zirconate thin films

In recent times antiferroelectric thin-film material compositions have been identified as one of the most significant thin films for development of devices such as high charge storage, charge couplers/decouplers, and high strain microelectromechanical systems. Thus, understanding the dielectric and electrical properties under an ac signal drive in these antiferroelectric thin-film compositions, such as lead zirconate thin films, and the effect of donor doping on them is very necessary. For this purpose, thin films of antiferroelectric lead zirconate and La-modified lead zirconate thin films with mole % concentrations of 0, 3, 5, and 9 have been deposited by pulsed excimer laser ablation. The dielectric and hysteresis properties have confirmed that with a gradual increase of the La content, the room-temperature antiferroelectric lead zirconate thin films can be modified into ferroelectric and paraelectric phases. ac electrical studies revealed that the polaronic related hopping conduction is responsible for the charge transport phenomenon in these films. With a La content of less than or equal to3 mole % in pure lead zirconate, the conductivity of the films has been reduced and followed by an increase of its conductivity for a greater than or equal to3% addition of La to lead zirconate thin films. The polaronic activation energies are also found to follow a similar trend as that of the conductivity.

Reversible and irreversible switching processes in pure and lanthanum modified lead zirconate thin films

The mechanism of field induced phase switching in antiferroelectric lead zirconate and La-modified lead zirconate thin films has been analysed in terms of reversible and irreversible switching process under weak fields as a function of donor concentration. Extension of Rayleigh law of ferromagnetic materials to the present antiferroelectric and modified antiferroelectric compositions have clearly showed that origin of small signal dielectric permittivity is due to reversible domain wall motion. Rayleigh's constant, a measure of irreversible switching process, exhibited a slight increase with lower La 3+ concentrations and followed by a gradual fall for higher concentration. This clearly illustrates that donor addition to antiferroelectric thin films controls the domain switching even under weak fields.

Preparation and Characterization of Antiferroelectric PZT Thin Films on Steel Substrates Using Intermediate Oxide Layers

Antiferroelectric lead zirconate titanate PZT (95/5) has been prepared by chemical solution deposition using alkoxide precursor compounds and was spin-coated on metallic substrates of Hastelloy. In order to better adapt the substrate to the PZT and thus to improve the crystallization behavior of the PZT films, different interface layers have been studied. The annealing parameters have been optimized in the case of an intermediate RuO 2 layer. Other interface layers like indium tin oxide (ITO) or lanthanum strontium manganate (LSMO) can be compared to deposition of the PZT on Hastelloy and on platinum coated Hastelloy. Using conventional multi-coating technique, homogeneous antiferroelectric films of up to 2.5 w m thickness have been obtained.

Preparation of antiferroelectric lead zirconate titanate stannate ceramics by high-energy ball milling process

Lead zirconate titanate stannate powders doped with lanthanum and niobium, namely [Pb0.99Nb0.02(Zr0.85Sn0.13Ti0.02)0.98O3, or PNZST) and (Pb0.9La0.02(Zr0.65Sn0.31Ti0.04)O3, or PLZST], were synthesized by a high-energy ball milling technique from their corresponding oxide mixtures. The milled powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle size analysis techniques. The sintering behaviors of the milled powders were investigated by a dilatometer from room temperature to 1100 °C. PZST ceramics formed from the high-energy ball milled powders were sintered at temperatures from 900 °C to 1200 °C. The measured electrical properties of the PZST ceramics were comparable to the results reported in the literature. These results have shown that the high-energy ball milling technique is a promising method to prepare PZST ceramics due to its simple procedure.

Preparation of antiferroelectric PbZrxTi1−xO3 thin films on LaSrMnO3-coated steel substrates

Antiferroelectric lead zirconate titanate (PZT) thin films have been prepared by chemical solution deposition using oxide powders. The films were processed onto steel substrates coated with a conducting oxide layer of LaSrMnO3. Homogeneous and uniform films up to 3.4 μm thick and with polarization saturation values up to 35 μC/cm2 have been obtained. The compositional transition from the ferroelectric to the antiferroelectric phase at the high zirconium side of the PZT phase diagram was studied by x-ray diffraction and hysteresis loop measurements as a function of the Zr/Ti ratio. Film thickness and annealing temperature dependencies are reported.