Lanthanum-doped Lead Zirconate Titanate Research Articles

Processing and electromechanical properties of lanthanum-doped Pb(Zr,Ti)O3 extruded piezoelectric fibres

This article describes the processing and characterisation of lanthanum-doped lead zirconate titanate (PLZT)-based ferroelectric fibres for composite transducer applications. X-ray diffraction of the extruded and sintered fibres indicated some lead loss during sintering; however, the fibres exhibited low porosity (1.54%), high maximum piezoelectric strain (4041 ppm) and relatively low coercive field (0.77 kV/mm). The low coercive field of the lanthanum-doped fibres may be advantageous in terms of facilitating polarization of the fibres in composite architectures.

Study on the characteristics of ferroelectric electron emission

Electron emission from ferroelectric cathodes is commonly suggested as an electron source for different applications due to its special characteristics such as high current density, easy treatment and operation. In this experimental research, the electron emission properties of ferroelectric cathodes made of lanthanum-doped lead zirconate–titanate (PLZT) ceramic are studied. The electron beam spot shape was recorded via proximity-imaging techniques.

In situneutron diffraction study of electric field induced structural transitions in lanthanum doped lead zirconate titanate

The structural reaction of La-doped PbZr1–xTixO3 (PLZT) with x = 0.44, 0.46 and 0.475 to an electric field was investigated by in situ neutron diffraction. The induced structural changes and the anisotropic displacement parameters were analysed. While the composition with a high Ti content shows a trend to tetragonal characteristics, PLZT with a low Ti content exhibits a rhombohedral response to the applied electric field. The intermediate composition with x = 0.46 appears rhombohedral in the unpoled state. Under the influence of an applied electric field, however, the response is similar to tetragonal PLZT (x = 0.475). With the investigated compositions the field induced processes are characterised. In the tetragonal composition the field dependent variation of the tetragonal lattice distortion is most pronounced. In rhombohedral PLZT (x = 0.44) the pseudorhombohedral lattice distortion exhibits the most significant changes. In the intermediate composition primarily atomic displacements are involved. Hence, a systematic change of the response to an applied electric field is observed while crossing the morphotropic phase boundary.

Sol-Gel Derived Nanocrystalline Lanthanum Doped Lead Zirconate Titanate Thin Films Studied for Solitary Waves Propagation

Nanocrystalline PLZT thin films of composition Pb1-xLaxZr0.52Ti0.48 (x = 0, 2, 5%) were deposited on silicon substrates by sol-gel process using lead acetate trihydrate, lanthanum nitrate hydrate, zirconium propoxide and titanium propoxide as lead, lanthanum, zirconium and titanium precursor materials. Experimental studies have been made on solitary waves in 2 mol% lanthanum doped sol-gel derived lead zirconate titanate thin films. The solitary waves are generated under the influence of external alternating electric field, which has the same frequency as the external field. These solitary waves propagate through the thin film upto its boundary and then reflect back. The magnitude of the solitary waves attenuates as they move away from the electrodes and their phase reverses on reflection. For certain frequencies of the external electric field, solitary waves exhibit resonance effect. Distortion in hysteresis loops has been demonstrated on the basis of solitary waves propagation in the film having different electrode area.

Study of incommensurate phases in Lanthanum-doped zirconium-rich Lead Zirconate Titanate ceramics

The microstructure and nanostructure of zirconium-rich Pb(Zr,Ti)O3 ceramics doped with small amounts of La which are right at transition between the ferroelectric (FE) and antiferroelectric (AFE) orderings has been examined using Transmission Electron Microscopy (TEM) imaging and diffraction. In this region, the La doping frustrates the formation of simple FE or AFE phases and promotes long period ordered phases (2-3 nm) with ordering along <110> with unit cells incommensurate with the primitive cubic unit cell. We show that the domain structure in these materials is closely related to that previously observed in AFE PbZrO3. Moreover, precision measurements of crystallographic tilts at domain boundaries using Kikuchi diffraction methods also confirms the close relationship to PbZrO3. The domains also contain a nanostructure perpendicular to the long-period ordering direction, but the reasons for the appearance of this nanostructure remain unclear.

An analysis of domain reorientation in PLZT ceramics byin situRaman spectroscopy

An in situ Raman spectroscopy in a parallel y(z,z)y configuration was employed to investigate the domain reorientation of unpoled lanthanum-doped lead zirconate titanate (PLZT) ceramics under the dc electric field of 2000 V/mm. It was found that the relative intensity ratio IE(2TO)/IE(3TO+2LO)+B1 of Raman optical modes varied periodically by 180° with the polarized direction of the laser beam. The maximum change in the intensity ratio may be correlated with the extent of the polarization within the PLZT ceramics. Upon taking the effects of the long-range electric fields associated with the polar vibrations into consideration, a formula is developed to describe the variations in the intensity ratio IE(2TO)/IE(3TO+2LO)+B1, and the average orientation within the examined grain during the application of electric field is further evaluated to be ∼33.8°.

ChemInform Abstract: Preparation and Structural Characterization of Rare‐Earth Doped Lead Lanthanum Zirconate Titanate Ceramics.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Study of the radiation characteristics of a scanning laser with a YAG:Nd^3+ active element when it is pumped with linear arrays of laser diodes at a pulse-repetition rate of up to 400 Hz

This paper presents the results of an investigation of the radiation characteristics of a YAG : Nd laser with intracavity scanning of the radiation by means of an electrically controlled space-time light modulator based on the transparent electrooptic ceramic lanthanum-doped lead zirconate titanate (PLZT) and laser-diode pumping of the active element at a pulse-repetition rate of up to 400 Hz. It is shown that birefringence and thermal lensing in the active element begins to show up when the repetition rate is 300 Hz.

Influence of composition and pressure on the electric field-induced antiferroelectric to ferroelectric phase transformation in lanthanum modified lead zirconate titanate ceramics

The electric field-induced phase transformation behavior in lanthanum-doped lead zirconate titanate ceramics was examined by polarization versus electrical field (P-E) measurements carried out from room temperature to 130 degrees C and under hydrostatic pressures from 20 to 300 MPa. The samples with composition (Pb(1-x)La(x))(Zr(0.90)Ti(0.10))(1-x/4)O(3) [PLZT x/90/10; x = 2,3,4 at%] were prepared by the standard solid-state reaction method. The analysis at room temperature under atmospheric pressure showed that the increase in the lanthanum content induces a transformation from the typical ferroelectric hysteresis, observed for PLZT 2,3/90/10, to double-hysteresis loops, typical of antiferroelectric phases, for PLZT 4/90/10 under a strong electric field. Hydrostatic pressure- induced and temperature-induced ferroelectric (FE) to antiferroelectric (AFE) phase transformations were examined. The measured hysteresis loops indicated that the FE-AFE phase transformation depends on both temperature and hydrostatic pressure for PLZT 3/90/10. This composition, which is in a ferroelectric state at room temperature under atmospheric pressure, can be transformed into the antiferroelectric phase by the application of a hydrostatic pressure of 100 MPa or by increasing the temperature to around 90 degrees C. The PLZT 2/90/10 and 4/90/10 compositions displayed predominantly ferroelectric and antiferroelectric behavior, respectively, over the ranges of temperature and hydrostatic pressure examined in the present study.

Effect of Fe and Mn doping at B-site of PLZT ceramics on dielectric properties

Iron (Fe) and manganese (Mn) doped lead lanthanum zirconate titanate (PLZT) ceramic powders have been synthesized by high temperature solid-state reaction method. Preliminary X-ray structural analysis of the compounds shows the formation of tetragonal structure. Detailed dielectric studies of the compounds as a function of temperature (from 300K to 600 K) at frequency 10 kHz suggest that the compounds undergo a diffuse phase transition. The transition temperature shifts towards higher side with decreasing the Zr ratio. The activation energy (Ea) of the samples was calculated from the plot of AC conductivity vs inverse of absolute temperature. Diffusivity ( γ) study of phase transition of these compounds provided its value between 1 and 2, indicating the variation of degree of disordering in the system.

Unusual Polarization Ordering in Incommensurate Phases on Ferroelectric-Antiferroelectric Boundary in Lanthanum Doped Lead Zirconate Titanate

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Field-Induced Phase Transition in Antiferroelectric Creamics of (Pb, La)(Zr, Sn, Ti)O3

External field-induced phase transition in the lanthanum-doped lead zirconate titanate stannate antiferroelectric ceramics near morphotropic phase boundary were studied as a function of electric field and temperature. Upon application of an electric field to the antiferroelectric ceramics that was larger than the field of E AEF − FE , the sample underwent a phase transform from the antiferroelectric to ferroelectric phase, associated with an abrupt change in macroscopic properties. The polarization and longitudinal strain increased rapidly from zero to about 30 μC/cm2 and zero to about 0.35%, respectively. The dielectric constant decreased rapidly from 610 to about 320. At some thermal regions, the induced ferroelectric phase can remain metastable state when the electric field is removed. The metastable ferroelectric phase was unstable, which recovered to antiferroelectric phase with increasing temperature. Large charge release from remnant polarization of metastable ferroelectric phase was observed.

Preparation and structural characterization of rare-earth doped lead lanthanum zirconate titanate ceramics

A new preparation route towards rare-earth (RE) doped polycrystalline lead lanthanum zirconate titanate (PLZT) ceramics (RE = Y 3+, Nd 3+, Yb 3+), based on the use of doped lanthanum oxide or zirconia, is reported. Structural characterization by X-ray powder diffraction reveals that secondary phase formation can be substantially diminished in comparison to conventional preparation methods. The distribution of the rare-earth dopants was investigated as a function of concentration by static 207Pb spin echo NMR spectra, using Fourier Transformation of Carr–Purcell–Meiboom–Gill spin echo trains. For the Nd- and Yb-doped materials, the interaction of the 207Pb nuclei with the unpaired electron spin density results in significant broadening and shifting of the NMR signal, whereas these effects are absent in the diamagnetic Y 3+ doped materials. Based on different concentration dependences of the NMR lineshape parameters, we conclude that the structural role of the Nd 3+ dopants differs significantly from that of Yb 3+. While the Nd 3+ ions appear to be statistically distributed in the PLZT lattice, incorporation of Yb 3+ into PLZT appears to be limited by the appearance of doped cubic zirconia as a secondary phase.

Influence of low lanthanum doping on the electrical characteristics of PZT(53/47)

Lanthanum-doped lead zirconate titanate with compositions (Pb1−3/2x Lax)(Zr0.53Ti 0.47)O3 (0.001 ⩽ x ⩽ 0.02) have been synthesized by the sol–gel method. The effect of La3+-doping with regard to the development of the crystalline phase, microstructure, dielectric, ferroelectric and piezoelectric characteristics has been investigated. The various mechanisms by which the A-site aliovalent La3+-dopant influences the dielectric and piezoelectric characteristics have also been established.

Acoustic phonon mode anomalies in lanthanum doped lead zirconate-titanate relaxor ferroelectric ceramics

Lanthanum-doped lead zirconate titanate, PLZT-x/65/35 (x=8.0, 9.0, and 9.4), relaxor ferroelectric ceramics were investigated by the high resolution Brillouin light scattering spectroscopy in the temperature range from ∼870 down to ∼170 K. Broad anomalies were observed in the acoustic phonon mode velocity and related elastic stiffness coefficient showing minimum between ∼320–∼240 K. The deviation in the acoustic mode velocity from the high temperature linearity at the Burns temperature (TB∼720 K) and presence of a broad central peak in the temperature range 200≤T≤540 K were attributed to the dynamics of polar nanoregions with randomly oriented local polarization appearing due to site and/or charge disorder at both A- and B-sites of the ABO3 perovskite lattice. The presence of a new temperature point Td (∼575 K) was conclusively established in PLZT-x/65/35 relaxor ceramics.

Patterning of PLZT and PSZT thin films by excimer laser

The patterning of lanthanum-doped lead zirconate titanate (PLZT) and strontium-doped lead zirconate titanate (PSZT) thin films has been examined using a 5-ns pulsed excimer laser. Both types of film were deposited by rf magnetron sputtering with in situ heating and a controlled cooling rate in order to obtain the perovskite-structured films. The depth of laser ablation in both PSZT and PLZT films showed a logarithmic dependence on fluence. The ablation rate of PLZT films was slightly higher than that of PSZT films over the range of fluence (10–150 J/cm2) and increased linearly with number of pulses. The threshold fluence required to initiate ablation was ∼ 1.25 J/cm2 for PLZT and ∼ 1.87 J/cm2 for PSZT films. Individual squares were patterned with areas ranging from 10×10 μm2 up to 30×30 μm2 using single and multiple pulses. The morphology of the etched surfaces comprised globules which had diameters of 200–250 nm in PLZT and 1400 nm in PSZT films. The diameter of the globules has been shown to increase with fluence until reaching an approximately constant size at ≤ 20 J/cm2 in both types of film. The composition of the films following ablation has been compared using X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy.

Solid state NMR as a new approach for the structural characterization of rare-earth doped lead lanthanum zirconate titanate laser ceramics

To facilitate the design of laser host materials with optimized emission properties, detailed structural information at the atomic level is essential, regarding the local bonding environment of the active ions (distribution over distinct lattice sites) and their extent of local clustering as well as their population distribution over separate micro- or nanophases. The present study explores the potential of solid state NMR spectroscopy to provide such understanding for rare-earth doped lead lanthanum zirconate titanate (PLZT) ceramics. As the NMR signals of the paramagnetic dopant species cannot be observed directly, two complementary approaches are utilized: (1) direct observation of diamagnetic mimics using 45Sc NMR and (2) study of the paramagnetic interaction of the constituent host lattice nuclei with the rare-earth dopant, using 207Pb NMR lineshape analysis. 45Sc MAS NMR spectra of scandium-doped PLZT samples unambiguously reveal scandium to be six-coordinated, suggesting that this rare-earth ion substitutes in the B site. Static 207Pb spin echo NMR spectra of a series of Tm-doped PLZT samples reveal a clear influence of paramagnetic rare-earth dopant concentration on the NMR lineshape. In the latter case high-fidelity spectra can be obtained by spin echo mapping under systematic incrementation of the excitation frequency, benefiting from the signal-to-noise enhancement afforded by spin echo train Fourier transforms. Consistent with XRD data, the 207Pb NMR lineshape analysis suggests that statistical incorporation into the PLZT lattice occurs at dopant levels of up to 1 wt.% Tm 3+, while at higher levels the solubility limit is reached.

Piezoelectric Response of Lanthanum Doped Lead Zirconate Titanate Films for Micro Actuators Application

AbstractLa doped lead zirconate titanate (PLZT) films are prepared using a chemical solution deposition process. The effect of La substitution on the piezoelectric response was investigated to clear the possibility of the micro actuator application for the PLZT films. Nominal compositions of the 10% Pb excess PLZT precursor solutions were controlled like La/Zr/Ti= 0/65/35, 3/65/35, 6/65/35, and 9/65/35. These precursor solutions were deposited on the Ir/Ti/SiO2/Si substrates, and the thickness of the PLZT films was 2μm. 10 to 20- μm- diameter Pt top electrodes are formed with a sputtering and a photolithography process. The polarization- field (P-E) hysteresis curves and the longitudinal displacement curves were measured with a twin beam laser interferometer connected with a ferroelectric test system. With increasing La substitution amount, theP-Ehysteresis curves became slim shape, and remnant polarization (Pr) decreased. The hysteresis of the piezoelectric longitudinal displacement curves also decreased with increasing La substitution amount. The amount of the displacement under unipolar electric field showed a peak at La/Zr/Ti= 3/65/35. The calculated effective longitudinal piezoelectric constant (d33eff) is 129.2 pm/V at 3/65/35. This amount was relatively higher than that of PZT films at morphotropic phase boundary (MPB: 0/53/47) composition prepared the same film preparation process.

UV Laser Ablation of PLZT and PSZT Films

ABSTRACTThe ablation of strontium-doped lead zirconate titanate (PSZT) and lanthanum-doped lead zirconate titanate (PLZT) films has been examined using a 5 ns pulsed excimer laser. Individual squares were patterned with sides in the range of 10-30 µm using single and multiple pulses. The depth of ablation in PLZT films was higher at all fluences than in PSZT films. The morphology of the etched surfaces has comprised the formation of globules which had diameters of 200-250 nm in PLZT and 1400-1600 nm in PSZT films. The diameter of the globules has been shown to increase with fluence until reaching an approximately constant size at &gt;20 J/cm2 in both types of film. The composition of the films following ablation has been analyzed using x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray (EDX) spectroscopy.

Metastable ferroelectric phase in lanthanum-doped lead zirconate titanate stannate antiferroelectric ceramics

Metastable ferroelectric phase induced by electric field in lanthanum-doped lead zirconate titanate stannate antiferroelectric ceramics near morphotropic phase boundary were studied as a function of electric field, temperature and hydrostatic pressure. Upon application of an electric field to the antiferroelectric ceramics, the rhombohedral FE phase can be induced from tetragonal AFE phase when the induced field was larger than the critical field E AEF-FE, and the induced FE phase can remain metastable state when the electric field was removed. The metastable FE phase was unstable, which recovered to AFE phase again with the increasing of temperature at about 80 °C and the increase of hydrostatic pressure at 150 MPa, respectively. Large charge release from remanent polarization of metastable FE phase was accompanied with phase transition. The relationships of critical parameters of field-induced phase transition were also shown.