Perovskite PZT Phase Research Articles

Role of Nb5+-Nd3+ co-dopant in morphotropic boundary of electrospun PZT nanoneedles: Study on dielectric and piezoelectric sensitivity

This study focused on the effects of individual and simultaneous modification of electrospun PZT nanostructures with doping by Niobium (Nb5+) and Neodymium (Nd3+) cations. The SEM, EDS, XRD, XPS, STA, and TEM analyses were performed to identify the role of the donor-acceptor on the morphology, crystallography, and morphotropic boundary (MPB) of PZT nanostructures. The results indicated that the nanowhiskers of PZT were formed after post-calcination at 800 ℃ for 2 h. The morphology of the nanowhiskers was not changed drastically with individual doping by Nb and Nd while co-doping caused to morphology switch to the nanoneedles. The perovskite PZT phase; Pb(Zr0.58Ti0.42)O3 (Zr-rich, rhombohedral) phase was achieved with doping by Nb, while Pb(Zr0.52Ti0.48)O3 (Ti-rich, tetragonal) was determined with doping by Nd. With the de-convolution of the Zr 3d spectrum of XPS, it was exhibited that the nearest composition to MPB was attributed to Nb-Nd co-doped PZT. The polycrystalline fiber arranged by tetragonal-rhombohedral was observed. It was also found that the concentration of oxygen vacancy was reduced with doping by Nb, while increased with doping by Nd. The dielectric properties of un-doped and doped PZT were investigated. The dielectric constant of PZT was increased with individual doping by Nb and Nd, while due to the donor-acceptor couple, a synergistic effect was observed for co-doping by Nb-Nd where maximum dielectric was 16 times higher than the un-doped PZT. Also, with measuring the output voltage, the highest piezoelectric sensitivity was observed in the Nb-Nd co-doped PZT sample. Our findings highly suggest the electrospinning method for achieving the nanostructured PZT to be employed in a variety of applications needs a high dielectric constant.

Synthesis, Structural, Optical and Dielectric Properties of Nanostructured 0-3 PZT/PVDF Composite Films.

Nanostructured PbZr0.52Ti0.48O3 (PZT) powder was synthesized at 500 °C-800 °C using sol-gel route. X-ray diffraction and Rietveld analysis confirmed the formation of perovskite structure. The sample heat treated at 800 °C alone showed the formation of morphotropic phase boundary with coexistence of tetragonal and rhombohedral phase. The PZT powder and PVDF were used in 0-3 connectivity to form the PZT/PVDF composite film using solvent casting method. The composite films containing 10%, 50%, 70% and 80% volume fraction of PZT in PVDF were fabricated. The XRD spectra validated that the PZT structure remains unaltered in the composites and was not affected by the presence of PVDF. The scanning electron microscopy images show good degree of dispersion of PZT in PVDF matrix and the formation of pores at higher PZT loading. The quantitative analysis of elements and their composition were confirmed from energy dispersive X-ray analysis. The optical band gap of the PVDF film is 3.3 eV and the band gap decreased with increase in volume fraction of PZT fillers. The FTIR spectra showed the bands corresponding to different phases of PVDF (α, β, γ) and perovskite phase of PZT. The thermogravimetric analysis showed that PZT/PVDF composite films showed better thermal stability than the pure PVDF film and hydrophobicity. The dielectric constant was measured at frequency ranging from 1 Hz to 6 MHz and for temperature ranging from room temperature to 150 °C. The composite with 50% PZT filler loading shows the maximum dielectric constant at the studied frequency and temperature range with flexibility.

Pulsed laser deposition of piezoelectric lead zirconate titanate thin films maintaining a post-CMOS compatible thermal budget

Integration of lead zirconate titanate (Pb[Zrx,Ti1-x]O3 – PZT) thin films on complementary metal-oxide semiconductor substrates (CMOS) is difficult due to the usually high crystallization temperature of the piezoelectric perovskite PZT phase, which harms the CMOS circuits. In this work, a wafer-scale pulsed laser deposition tool was used to grow 1 μm thick PZT thin films on 150 mm diameter silicon wafers. Three different routes towards a post-CMOS compatible deposition process were investigated, maintaining a post-CMOS compatible thermal budget limit of 445 °C for 1 h (or 420 °C for 6 h). By crystallizing the perovskite LaNiO3 seed layer at 445 °C, the PZT deposition temperature can be lowered to below 400 °C, yielding a transverse piezoelectric coefficient e31,f of −9.3 C/m2. With the same procedure, applying a slightly higher PZT deposition temperature of 420 °C, an e31,f of −10.3 C/m2 can be reached. The low leakage current density of below 3 × 10−6 A/cm2 at 200 kV/cm allows for application of the post-CMOS compatible PZT thin films in low power micro-electro-mechanical-systems actuators.

X-Ray Diffraction and Zn K-Edge XANES Studies of Perovskite Ferroelectric PZT-PZN Powders Derived from Zn2Nb34O87 Precursor

An approach to synthesize perovskite ferroelectric 0.9Pb(Zr0.44Ti0.56)O3-0.1Pb(Zn0.33Nb0.67)O3 or 0.9PZT-0.1PZN powders with a modified mixed-oxide synthetic route via a combination of the perovskite PZT phase stabilizer and the novel intermediate phase of Zn2Nb34O87 B-site has been developed. Phase formation, morphology, particle size, chemical composition and oxidation state of the products were investigated as a function of calcination temperatures. It has been found that the pyrochlore phase of Pb3Nb4O13 tends to form together with the perovskite phase of PZT-PZN, depending on calcination temperatures. It is seen that optimization of calcination condition can lead to a 100% yield of PZT-PZN in a tetragonal perovskite phase. The tetragonality factor, degree of agglomeration, crystallite size and average particle size tend to increase with the calcination temperatures. In addition, the synchrotron X-ray absorption near edge structure (XANES) analysis showed the oxidation state of Zn2+ atoms for all condition of 0.9PZT-0.1PZN powders.

Synthesis and Characterization of Lead Zirconate Titanate Nanofibers Obtained by Electrospinning

In this study, lead zirconate titanate (PZT) nanofibers were synthesized by electrospinning method using polyvinylpyrrolidone (PVP) as a viscosity controller and were characterized the crystallinity and the chemical composition ofPZTnanofibers obtained by different postannealing methods. From the X‐ray photoelectron spectroscopy results, the formation ofPZTnanofibers was confirmed. The diameter ofPZTnanofibers was a few hundreds of nanometers. And the diameter ofPZT‐D (directly annealed to the target temperature) nanofibers decreased as the annealing temperature increased while the diameter ofPZT‐S (stepwisely annealed to the target temperature) nanofibers increased which were confirmed bySEM. According to the results of X‐ray diffraction, as the annealing temperature increased, the crystallinity ofPZTnanofibers changed from pyrochlore to perovskite structure and the perovskite phase ofPZTwas observed from thePZTnanofibers annealed at823 K.

Rapid thermal processing of electrospun PbZr0.52Ti0.48O3 nanofibers

Electrospinning is potentially an effective way to prepare ceramic nanofibers using sol–gel precursors. However, the raw dried fibers require a sintering step that can lead to highly porous nanofibers or to a total loss of the fiber morphology. Generating dense sintered nanofibers via electrospinning is challenging, particularly in PZT fibers, where lead loss at high temperatures is amplified due to the large surface. This paper focuses on rapid thermal processing (RTP) of PZT nanofibers. The fibers thermal decomposition is studied in detail by TGA/DTA combined with mass spectroscopy and XRD. Pre-firing at 350°C for 0.5h is required for effective organics burnout. RTP for 30s at 800°C allows formation of the perovskite PZT phase, similar to conventional firing at 650°C for 2h. In summary, we demonstrated that a combination of pre-firing with RTP sintering can be used as an efficient and environmentally friendly process, leading to dense, smooth PZT nanofibers that are sensitive to deformation.

A Study of Pb (Zr<sub>0.52</sub>Ti<sub>0.48</sub>)O<sub>3</sub> Ceramic Properties via High Energy Ball Mill

Pb (Zr0.52Ti0.48)O3, (PZT) powder has been synthesized using high energy ball milling technique. The synthesized powders were characterized using XRD, SEM, Density, Porosity and Impedance Analyzer. XRD patterns show that the perovskite phase of PZT can be formed from the mixture of starting material after milling for 40 h. The grain sizes of the powder have been estimated to be 1-3 μm. The relationship between the microstructure of the PZT samples and sintering temperature has been discussed. Dense PZT (> 95 % theoretical density) with excellent dielectric properties was obtained when the pellet are sintered at higher temperature with shorter soaking time. The results show that the sample sintered at 1100 °C /1 h yields a clearly uniform grain size with the highest dielectric constant.

Influence of annealing temperature on Pb(Zr,Ti)O3 nanoparticles growth on multi-walled carbon nanotubes

We report the influence of annealing temperature on Pb(Zr,Ti)O3 nanoparticles (PZT NPs) grown on multi-walled carbon nanotubes (MWCNTs). The nanocomposites consist of PZT NPs and MWCNTs that were successfully prepared by using a sol-gel process, followed by an injection using a syringe filter and then by rapid thermal annealing. Field-emission transmission electron microscopy (FETEM) indicated that as the annealing temperature was increased, the shape and the crystallinity of the PZT NPs on the MWCNTs changed from an amorphous structure to the perovskite phase of PZT. Raman spectroscopy showed that the ratio of the intensity of G band to that of the D band, which indicates the crystal purity of the MWCNTs, decreased from 0.57 to 0.55 when the annealing temperature was increased from 500 to 700 °C. A separate distribution of elemental C in the PZT NPs on the MWCNTs annealed at 600 °C was directly observed via energy dispersive X-ray spectroscopy.

Synthesis of Crack-Free PZT thin Films by Sol-gel Processing on Glass Substrate

PZT thin films deposited on glass substrates have been proposed for many applications such as adjustable optics in future X-ray telescopes. Sol-gel method is widely utilized to prepare PZT thin films due to its low reaction temperature, uniform mixing of reactants, and precise control of component. Crack-free transparent PZT thin films were prepared by dip-coating the solutions of complex alkoxides. PZT thin films were calcined at various temperatures and characterized by X-ray diffraction, field emission scanning electron microscopy to examine the surface morphology, and FT-IR spectroscopy. The XRD analysis confirmed the formation of perovskite phase at 600°C. FE-SEM results showed nucleation of PZT perovskite phase. Furthermore, the average grain size was measured in the range of 55 to 190nm.

Percolative nanoparticle-Ag/PbZr0.52Ti0.48O3 composite thin film with high dielectric and ferroelectric properties

Agx/PbZr0.52Ti0.48O3 (PZT, x defined as mole ratio of Ag/Pb) composite thin films were fabricated by the sol–gel technique. Results showed that the Agx/PZT thin films were composed of perovskite phase of PZT and silver nanoparticles. The silver nanoparticles with size between 4.5 and 7 nm were uniformly dispersed in the thin films. The percolation behavior occurred in the Ag/PZT thin films. The properties of PZT thin film were significantly improved as silver was introduced, especially as the fraction of silver nanoparticles was near the percolation threshold. The relative permittivity of the percolative Ag0.7/PZT thin film was 230 % higher than that of the single phased PZT thin film. The tunability of the percolative Ag0.7/PZT thin film was 57 % higher than that of the single phased PZT thin film. Meanwhile, the operating voltage for Ag0.7/PZT thin film supplying optimal tunability was only ~3 V (120 kV/cm), which was reduced by about 45 % compared to the single phased PZT thin film. The remanent polarization value of the Ag0.7/PZT percolative thin film was 22.9 μC/cm2, which was about 26 % higher than that of the single phased PZT thin film. While the coercive field of the Ag0.7/PZT percolative thin film was reduced by 29 %. It is attractive to be used as an electronic thin film with high performance.

Ferroelectric hysteresis and improved fatigue of PZT (53/47) films fabricated by a simplified sol–gel acetic-acid route

Double-layer Pb(Zr0.53Ti0.47)O3 films were fabricated by spin coating of a sol–gel acetic-acid-based precursor solution deposited onto commercial Pt–Si substrates. The structural properties of the samples were studied by several diffraction, spectroscopy and microscopy techniques. The annealed ferroelectric films were crystallized to a pure PZT perovskite phase. A significant monoclinic phase content was found together with a relatively large tetragonal c/a ratio, according to the diffraction pattern refinement results. No traces of organic material were observed. Good film densification with relatively large grain sizes and low surface roughness was achieved. Ferroelectric domain distribution and local piezoresponse hysteresis loops were investigated by piezoresponse force microscopy. The films showed good local ferroelectric properties and a relatively large d33 piezoelectric coefficient was derived. A degree of self-polarization of the film was also found from the domain distribution-map analysis. Good macroscopic ferroelectric properties were also achieved, specially for the film with less rhombohedral content. An improved ferroelectric fatigue behavior was observed as the films proved to sustain down to 108 fatigue cycles with only a 10 % decrease of the initial remnant polarization.

High resolution X-ray and electron microscopy characterization of PZT thin films prepared by RF magnetron sputtering

Pb(Zr0.52Ti0.48)O3 (PZT) thin films grown on Pt/TiO2/SiO2/Si(1 0 0) substrates in the thickness range of ∼30–550 nm by radio frequency (RF) magnetron sputtering method under different sputtering pressures were studied in the present work. High resolution grazing incidence X-ray diffraction method for residual stress and electron microscopy, particularly cross sectional transmission electron microscopy (XTEM), were used to identify the crystalline phases, and structure of the thin films at the nano-scale. Microstructure of the ultrathin films in <50 nm thickness range, consists predominantly of para-electric, oxygen deficient pyrochlore phase of Pb2Ti2O6 structure co-existing with ferroelectric perovskite PZT phase in tetragonal form. In films with thickness around 500 nm, sputtering pressure shows a strong influence on the purity of PZT phase grown. High resolution X-ray diffraction method for wafer curvature measurement and Stoney's equation were used to evaluate the biaxial stress in the films. It is found that the ultrathin films are compressively stressed with high magnitude of the order of 2 GPa which gets reduced with increasing film thickness. In the thickness range of ∼500 nm, at an optimum sputtering pressure of 4.5 Pa, the stress becomes tensile in nature with a small magnitude of 2.3 MPa. At this pressure, the film consists of almost pure perovskite phase and comparatively better electrical characteristics. X-ray reflectometry study indicates very low density of PZT films with an interlayer formed at the interface with Pt. XTEM study throws valuable insight into the nano-scale structure and reveals the presence of nano-porosity along the interface as well as within the film microstructure. This has been attributed to the observed interface roughness, reduced density, tensile residual stress as well as the poor ferroelectric properties encountered.

Effect of Switching Atmospheric Conditions during Crystallization on the Phase Evolution of Solution‐Derived Lead Zirconate Titanate Thin Films

The crystallization behavior of solution‐derived lead zirconate titanate (PZT) thin films in different atmospheric environments was studied using in situ X‐ray diffraction. The stability of the transient intermetallic Pt3Pb phase and perovskite PZT is dependent on oxygen partial pressure during crystallization. Based on the relationship between oxygen partial pressure and the resultant phase stability of intermediate phases, a new route to produce PZT thin films was developed. The new route involves switching atmospheres during crystallization and is shown to mitigate the formation of the transient intermetallic Pt3Pb phase and to promote the perovskite PZT phase. The route evidences a new and significant variable controlling film synthesis and film microstructure.

Effect of heating rate on microstructure and electrical properties of sol–gel derived lead zirconate titanate films crystallized by rapid thermal annealing

In the present work, Ferroelectric Lead zirconate titanate [Pb(ZrxTi1-x)O3: PZT] films with a nominal formula Pb1.1(Zr0.52Ti0.48)O3 were prepared with the sol–gel method and post-annealed by rapid thermal annealing. Different heating rates were adopted to explore their effect on microstructure and electrical properties of PZT films. The results show that heating rate has a significant effect on the orientation and grain size distribution of PZT films under the same annealing temperature, which further results in different dielectric and ferroelectric properties. It is found that the faster heating rate is not favorable for enhancing the ferroelectricity of PZT films although it promotes the phase transition process. The relationship between heating rate and microstructure of PZT films is discussed based on its effect on the nucleation and growth process of PZT perovskite phase. It is proposed that the nucleation and growth process of perovskite phase occurs under different stress states at different heating rates, which leads to the varying orientations of films.

Effects of ZnO nanoneedles addition on the mechanical and piezoelectric properties of hard PZT-based composites

Hard PZT (PZT4)-based composites embedded by ZnO nanoneedles (denoted as PZT/ZnOn) were fabricated by a solid state sintering technique. The characteristic diffraction peaks of the perovskite PZT and ZnO phases were identified from the studied composites, indicating the retention of ZnOn. With increasing ZnOn content, the grain size of the composites was reduced gradually. In contrast with the pure PZT, the PZT/ZnOn composites possessed more excellent mechanical properties, while the piezoelectric properties were reduced by a certain extent. The best mechanical properties of PZT/ZnOn composites were obtained by sintering at 1,150 °C with 1.5 wt% ZnO nanoneedles addition: fracture toughness K IC ~ 2.04 MPa m1/2, flexural strength σ f ~ 105.44 MPa, compressive strength σ c ~ 543.89 MPa. The piezoelectric properties of the PZT/ZnOn composites were found to be lower than that of the pure PZT with dielectric permittivity e r of 768–893, piezoelectric coefficient d 33 of 240–260pC/N, mechanical quality factor Q m of 340–650 and planar electromechanical coupling k p of 0.5–0.55.

Pb(Zr&lt;sub&gt;0.52&lt;/sub&gt;Ti&lt;sub&gt;0.48&lt;/sub&gt;)O&lt;sub&gt;3&lt;/sub&gt; Ceramics Synthesized Using Planetary Ball Mill

Lead zirconate titanate Pb (Zr0.52Ti0.48)O3, (PZT) ceramic was successfully prepared from the mixture of commercial PbO, TiO2 and ZrO2 powders using planetary ball mill at room temperature. The phase formation and microstructure of the milled powders were characterized using X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). XRD results indicated that the perovskite phase of PZT was formed from the mixture of starting materials after milling for 40 h. The grain sizes of the powders have been estimated from the SEM images to be ~200 nm. The compacted PZT samples were then sintered at 950 °C for 1 h. The samples were characterized by XRD and SEM, meanwhile the density was measured by Archimedes principle. XRD analysis on the sintered samples revealed the formation of single phase Pb (Zr0.52Ti0.48)O3 ceramics while the SEM images estimated the grain size to be ~2 µm. The relative density of the obtained sintered PZT ceramics was measured to be approximately 99.93 % of the theoretical density. The results hence indicate that planetary ball mill is an effective preparatory technique to improve the sinterability of PZT ceramics.

Synthesis and Characterization of Nanocrystalline PZT Powders by a Simple Sol-Gel Method

Nanocrystalline lead zirconate titanate (PZT) powders with composition at the morphotropic phase boundary (MPB) were synthesized by a simple aqueous based sol-gel method, using lead nitrate, zirconium nitrate and tetrabutyl titanate as the starting materials. The sol could be easily transformed into gel, firstly heated at 120°C for 10h, then at 180°C for 24h. The thermal decomposition process of the gel was investigated by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. The effect of citrate addition amount on the calcining temperature was discussed. The results reveal that pure perovskite phase PZT powders can be obtained at a calcining temperature as low as 600°C. The average grain size of the powders was determined by transmission electron microscope and X-ray diffraction. The influences of calcining temperature and the pH value of the solution on the grain size were investigated. The sintering temperature and electrical properties of the ceramics derived by nano-powders were compared with those prepared by the conventional ceramic processing. The result shows that using the nanopowder, the sintering temperature could be reduced by about 100°C and the ferroelectric properties were enhanced.

Influence of buffer layer on structural, electrical and mechanical properties of PZT/NiTi thin film heterostructures

Ti and TiN layers of 8–10nm thickness were employed as a buffer layer to improve the structural, electrical and mechanical properties of Pb(Zr0.52Ti0.48)O3(PZT)/NiTi heterostructures synthesized using dc/rf magnetron sputtering. The buffer layers were deposited on NiTi prior to the growth of PZT films. It was observed that the incorporation of buffer layer favored the formation of single perovskite PZT phase with no evidence of pyrochlore phase. Further, the properties of these heterostructures were observed to change with corresponding change in crystalline orientation of top PZT layer. The PZT/NiTi heterostructures with additional buffer layer exhibited enhanced remnant polarization (Pr) and dielectric constant (ε). A sudden increment in the dielectric constant was observed for PZT/buffer/NiTi heterostructures near room temperature. This could be attributed to the increasing ionic displacement of Ti ion with respect to the O ion in PZT films due to the stress induced by the martensite variants of NiTi layer during phase transformation from a low temperature martensite phase to high temperature austenite phase. This transformation promotes the strain-induced polarization and henceforth enhancing the dielectric constant of PZT films. Nanoindentation studies indicate the maximum hardness of 7.6GPa and indentation modulus of 206GPa for PZT(111)/TiN/NiTi heterostructure.

Role of TiO2 Seed Layer Thickness on the Nanostructure Evolution and Phase Transformation Behavior of Sputtered PZT Thin Films During Post‐Deposition Air‐Annealing

An optimum TiO2 seed layer is said to facilitate nucleation and subsequent growth of perovskite phase in Pb(Zr,Ti)O3 (PZT) films during annealing. The actual causes that prevent perovskite growth, particularly in sputtered PZT films on thick TiO2 seed layers are not yet understood clearly. Herein, based on the results of X‐ray diffractometry (XRD), field‐emission scanning electron microscopy (FESEM), and analytical scanning/transmission electron microscopy (S/TEM) with semi‐quantitative elemental mapping using energy dispersive X‐ray (EDX) spectrum imaging, the post‐annealing crystallization trend of r.f. magnetron sputter‐deposited amorphous PZT films has been scrutinized as a function of TiO2 seed layer thickness. Upon annealing, PZT films on thin TiO2 layers (~20–100 nm) partially crystallize into perovskite PZT via a transient pyrochlore/fluorite phase. However, no perovskite phase forms on thicker (~550 nm) TiO2 layer. Thickness of underlying TiO2 seed layer strongly influences the crystallization, phase formation, texture, and surface morphology of the PZT films. During crystallization, Pb diffuses away from the PZT film to form solid solution with TiO2 seed layer. Perovskite PZT phase transformation requires a minimum Pb‐concentration within the transient pyrochlore/fluorite phase. During the growth of perovskite grains, Zr gets segregated, resulting in Zr‐concentration build‐up within the surrounding disordered fcc fluorite phase.

Fabrication and magnetic properties of composite Ni0.5Zn0.5Fe2O4/Pb(Zr0.52Ti0.48)O3 nanofibers by electrospinning

One-dimensional and quasi-one-dimensional nanostructure materials are promising building blocks for electromagnetic devices and nanosystems. In this work, the composite Ni0.5Zn0.5Fe2O4(NZFO)/Pb(Zr0.52Ti0.48)O3(PZT) nanofibers with average diameters about 65 nm are prepared by electrospinning from poly(vinyl pyrrolidone) (PVP) and metal salts. The precursor composite NZFO/PZT/PVP nanofibers and the subsequent calcined NZFO/PZT nanofibers are investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM).The magnetic properties for nanofibers are measured by vibrating sample magnetometer(VSM). The NZFO/PZT nanofibers obtained at calcination temperature of 900 °C for 2 h consist of the ferromagnetic spinel NZFO and ferroelectric perovskite PZT phases, which are constructed from about 37 nm NZFO and 17 nm PZT grains. The saturation magnetization of these NZFO/PZT nanofibers increases with increasing calcination temperature and contents of NZFO in the composite.