Strontium-doped Lead Zirconate Titanate Research Articles

Nanoindentation response of piezoelectric nano-islands

Through three-dimensional finite element modeling, it is demonstrated that the nanoindentation response of piezoelectric nano-islands is strongly dependent on the shape of the nano-island and the depth of indentation. For indentations that are relatively deep (i.e., greater than 5% of the height of the islands), the substrate's elastic and plastic properties have a strong influence on the indentation response of piezoelectric nano-islands with substrate plasticity resulting in a significant reduction in the mechanical and electrical indentation stiffness. The predictions of the finite element models compare well with experiments on nano-islands of strontium-doped lead zirconate titanate.

Correlation between nanomechanical and piezoelectric properties of thin films: An experimental and finite element study

Piezoelectric materials perform mechanical-to-electrical energy conversion and have unique and enhanced properties, particularly in the thin film form. In this work, the nanomechanical properties of strontium-doped lead zirconate titanate thin films are investigated by nanoindentation. Finite element modeling of the nanoindentation process allows for a comparison of the simulated and experimentally measured load–displacement curves. New insights correlating the nanomechanical and piezoelectric properties of thin films have been obtained which will enable more efficient design of piezoelectric energy harvesting devices.

Synthesis of Phase Pure Strontium Doped Lead Zirconate Titanate Nano Crystalline Powder by Sol-Gel Approach

Phase pure Strontium doped PZT (Pb0.96Sr0.04Zr0.53Ti0.47O3) was synthesized by sol gel process. Zirconium and Titanium alkoxides were used as starting materials and Lead (II) Acetate trihydrate was used as Pb source. The alkoxides mixture was stabilized by acetylacetonate. The vacuum dried gel was calcined at different temperatures to study the calcination temperature and the resulting samples were analyzed by DSC, TG and XRD. The powder remained amorphous until a temperature of 550°C. The morphology and composition of the powder was studied using EDX, stereomicroscope and high resolution SEM.

Strontium Doped Lead Zirconate Titanate Ceramics: Study of Calcination and Sintering Process to Improve Piezo Effect

Perovskite crystal structure is found in many ionic solids like CaTiO3, BaTiO3 and Lead Zirconate Titanates (PZT). In this structure off-center position of cations in oxygen octahedral causes polarization and produces direct and indirect piezoelectric responses in ceramic materials that are suitable for many ultrasonic applications. In the present study 9% Sr doped PZT ceramics were prepared and their dielectric and piezoelectric properties measured. X ray Diffraction (XRD) analysis of calcined powders demonstrated a decrease in the PbO content during the calcination stage at 850 degrees C. This was counterbalanced by adding excess PbO at the time of preparation of mixtures. Sintering was carried out at 1200 degrees C for 2 hours in lead rich atmosphere. The properties achieved were Dielectric Constant (K) = 1440, Tangent Loss (Tan delta) = 0.0062, Charge Coefficient (d33) = 335 pC/N and density = 7.55 g/cm3. SEM analysis of sintered samples demonstrated that grain size was 2-3 microm with clean grain boundaries and no large size porosity observed. XRD analysis of sintered pellets exhibited that material prepared was free of any precipitated phase usually harmful for the piezo effect.

Effect of temperature on polarization reversal of strontium-doped lead zirconate titanate (PSZT) ceramics

The effect of temperature on polarization reversal of strontium-doped lead zirconate titanate ceramics was studied. The piezoelectric properties viz. dielectric constant and piezoelectric coupling coefficient, were used for polarization reversal characteristic. These properties and apparent coercive field were measured during polarization reversal at different temperatures. Results indicated that at higher temperature apparent coercive field decreased. Polarization reversal and further polarization reversal was quite asymmetric. After polarization reversal, dielectric constant was found to increase at all temperatures while piezoelectric coupling coefficient increased above the temperature of polarization. The trend shown by dielectric constant indicates that at 25°C, 1·5 kV/mm field can be applied safely to this material without much compromising the properties. D.c. field of 3·0 kV/mm and 100°C temperature can be predicted as poling parameters from their effect on \({\bf \textit{k}}_{{\bf p}}\). Apparent coercive field has shown non-linear relationship with temperature. It was of exponential decay type.

Island Structured Dielectric Thin Films by Scalable Self-Assembly

AbstractA self-assembly driven process to synthesize island-structured dielectric films is presented. An intermetallic reaction in platinized silicon substrates provides preferential growth sites for the complex oxide dielectric (strontium-doped lead zirconate titanate) layer. Microscopy and spectroscopy analyses have been used to propose a mechanism for this structuring process. This provides a simple and scalable process to synthesize films with increased surface area for sensors, especially those materials with a complex chemistry.

Lattice Guiding for Low Temperature Crystallization of Rhombohedral Perovskite-Structured Oxide Thin Films

Low temperature crystallization of complex oxide thin films has proved to be a challenge with deposition of such materials often carried out at elevated temperatures in excess of 600 °C. This article demonstrates one of the first instances of deposition of preferentially oriented strontium-doped lead zirconate titanate thin films at a relatively low temperature of 300 °C. This was achieved by carrying out deposition on gold-coated silicon substrates which exert a guiding influence on thin film growth due to similarity in lattice parameters. The microstructure and preferential orientations were studied using high resolution transmission electron microscopy and X-ray diffraction. These results illustrated the pronounced texture in the deposited thin films due to lattice guiding, with crystal structure simulations also verifying the guiding effect.

Effect of electrical fatigue on the electromechanical behavior and microstructure of strontium modified lead zirconate titanate ceramics

The fatigue behavior of strontium doped lead zirconate titanate (PSZT) ceramics is investigated. Different compositions near the antiferroelectric–ferroelectric (AF–F) phase boundary are synthesized by tape casting and sintering route. The influence of electric field-induced AF to F phase transition on piezoelectric and strain behaviors is studied. Very high maximum polarization (∼41 μC/cm 2) and ultrahigh strain (0.8%) are seen for some of the PSZT compositions near the morphotropic phase boundary. The samples are subjected to low frequency (30 Hz) electric field up to 10 7 cycles. Although the maximum polarizations of most of the PSZT ceramics showed fatigue-free behavior (less than 10% degradation), the strains in most of them showed degradation as high as over 50%. Electron microscopy of the fractured surface of the electrically cycled samples showed some intergranular fracture below the electroded surface. Results indicated that diffusion of silver electrode into the PSZT ceramics is responsible for the electro-coloration and degradation in strain response with fatigue cycles. Thermal annealing and removal of the damaged layer under the electrode showed the complete recovery of the strain to its original as-sintered value. X-ray diffraction technique is used before and after the fatigue cycles to investigate the influence of electrical cycles on the changes at the crystal structure level, which are also related to the fatigue-induced changes to electromechanical properties of PSZT ceramics.

In situ investigation of thermally influenced phase transformations in (pb0.92sr0.08) (zr0.65ti0.35)o3 thin films using micro-raman spectroscopy and x-ray diffraction

Thin films of ferroelectric strontium-doped lead zirconate titanate [PSZT, (Pb(0.92)Sr(0.08))(Zr(0.65)Ti(0.35))O(3)] deposited by RF magnetron sputtering have been analyzed by in situ analysis techniques. The in situ techniques employed for this study include micro-Raman spectroscopy and X-ray diffraction (XRD), and variations in thin film structure and orientations for temperatures up to 350 degrees C and 750 degrees C for the respective techniques have been studied. The samples analyzed were PSZT thin films deposited on platinum-coated silicon substrates at either room temperature or at 750 degrees C. In situ measurements using micro-Raman spectroscopy and XRD techniques have been used to identify the Curie point for poly-crystalline PSZT thin films and to determine the temperature-activating significant grain growth for room-temperature-deposited PSZT thin films. To study the presence of hysteresis, analysis was carried out during both temperature ramp-up and ramp-down cycles. Raman measurements showed expected bands (albeit weak), and the in situ measurements have detected variations in the crystal structure of the thin film samples, with negligible variations between the heating and cooling cycles. A combination of the Raman and XRD results has shown that the temperature-activating significant grain growth for the room-temperature-deposited films is about 275 degrees C and the Curie point lies between 325 and 400 degrees C. This relatively high Curie point makes these films suitable for wide temperature range applications.

Microstructural and Compositional Analysis of Strontium-Doped Lead Zirconate Titanate Thin Films on Gold-Coated Silicon Substrates

This article discusses the results of transmission electron microscopy (TEM)-based characterization of strontium-doped lead zirconate titanate (PSZT) thin films. The thin films were deposited by radio frequency magnetron sputtering at 300 degrees C on gold-coated silicon substrates, which used a 15 nm titanium adhesion layer between the 150 nm thick gold film and (100) silicon. The TEM analysis was carried out using a combination of high-resolution imaging, energy filtered imaging, energy dispersive X-ray (EDX) analysis, and hollow cone illumination. At the interface between the PSZT films and gold, an amorphous silicon-rich layer (about 4 nm thick) was observed, with the film composition remaining uniform otherwise. The films were found to be polycrystalline with a columnar structure perpendicular to the substrate. Interdiffusion between the bottom metal layers and silicon was observed and was confirmed using secondary ion mass spectrometry. This occurs due to the temperature of deposition (300 degrees C) being close to the eutectic point of gold and silicon (363 degrees C). The diffused regions in silicon were composed primarily of gold (analyzed by EDX) and were bounded by (111) silicon planes, highlighted by the triangular diffused regions observed in the two-dimensional TEM image.

Nanocolumnar Preferentially Oriented PSZT Thin Films Deposited on Thermally Grown Silicon Dioxide

We report the first instance of deposition of preferentially oriented, nanocrystalline, and nanocolumnar strontium-doped lead zirconate titanate (PSZT) ferroelectric thin films directly on thermal silicon dioxide. No intermediate seed or activation layers were used between PSZT and silicon dioxide. The deposited thin films have been characterised using a combination of diffraction and microscopy techniques.

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.

Effect of multi-layered bottom electrodes on the orientation of strontium-doped lead zirconate titanate thin films

This article discusses the results from X-ray diffraction (XRD) analysis of piezoelectric strontium-doped lead zirconate titanate (PSZT) thin films deposited on multi-layer coatings on silicon. The films were deposited by RF magnetron sputtering on a metal coated substrate. The aim was to exploit the pronounced piezoelectric effect that is theoretically expected normal to the substrate. This work highlighted the influence that the bottom electrode architecture exerts on the final crystalline orientation of the deposited thin films. A number of bottom electrode architectures were used, with the uppermost metal layer on which PSZT was deposited being gold or platinum. The XRD analysis revealed that the unit cell of the PSZT thin films deposited on gold and on platinum were deformed, relative to expected unit cell dimensions. Experimental results have been used to estimate the unit cell parameters. The XRD results were then indexed based on these unit cell parameters. The choice and the thickness of the intermediate adhesion layers influenced the relative intensity, and in some cases, the presence of perovskite peaks. In some cases, undesirable reactions between the bottom electrode layers were observed, and layer architectures to overcome these reactions are also discussed.

Thin film piezoelectric response characterisation using atomic force microscopy with standard contact mode imaging

This article introduces a technique for observing and quantifying the piezoelectric response of thin films, using standard atomic force microscopes (AFMs). The technique has been developed and verified using strontium-doped lead zirconate titanate (PSZT) thin films, which are known for their high piezoelectric response. Quantification of the electro-mechanical voltage coefficient d 33 (pm/V) is made directly based on the applied peak-to-peak voltage and the corresponding peak-to-peak displacement in the obtained scan image. Under the proposed technique the AFM is configured in contact mode, where the silicon nitride tip is set to follow the film displacement at a single point. A known sinusoidal voltage is applied across the film and the displacement determined as a function of time, rather than the typical AFM measurement of displacement versus tip position. The resulting raster image contains several bands, which are directly related to the AFM scan frequency and the applied sinusoidal voltage and its frequency. Different combinations of the AFM scan frequency and the applied sinusoid frequency have been used to characterise the PSZT thin films, with estimated values of d 33 between 109 and 205 pm/V.

Influence of oxygen partial pressure on the composition and orientation of strontium-doped lead zirconate titanate thin films

The influence of oxygen partial pressure during the deposition of piezoelectric strontium-doped lead zirconate titanate thin films is reported. The thin films have been deposited by RF magnetron sputtering in an atmosphere of high purity argon and oxygen (in the ratio of 9:1), on platinum-coated silicon substrates (heated to 650 °C). The influence of oxygen partial pressure is studied to understand the manner in which the stoichiometry of the thin films is modified, and to understand the influence of stoichiometry on the perovskite orientation. This article reports on the results obtained from films deposited at oxygen partial pressures of 1–5 mTorr. The thin films have been studied using a combination of X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GA-XRD), and atomic force microscopy (AFM). XPS analysis highlights the marked influence of variations in oxygen pressure during sputtering, observed by variations in oxygen concentration in the thin films, and in some cases by the undesirable decrease in lead concentration in the thin films. GA-XRD is used to study the relative variations in perovskite peak intensities, and has been used to determine the deposition conditions to attain the optimal combination of stoichiometry and orientation. AFM scans show the marked influence of the oxygen partial pressure on the film morphology.

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 >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.

Measurement of high piezoelectric response of strontium-doped lead zirconate titanate thin films using a nanoindenter

Strontium-doped lead zirconate titanate (PSZT) is reported to have a high piezoelectric coefficient (d33) in the range of 200−600 pm∕V, when in the form of ceramic disks or pellets. This article reports piezoelectric response results for PSZT thin films deposited by rf magnetron sputtering on gold-coated silicon substrates. The compositions of the deposited thin films have been found to be uniform with depth, using secondary ion mass spectroscopy. The surfaces of the deposited thin films have been studied using an atomic force microscope and observed to be regular and nanostructured in nature. The piezoelectric response of the thin films, using the inverse piezoelectric effect, has been measured using a nanoindenter. Values of thin film d33 up to 608 pm∕V were obtained, which is much higher than previously reported values of d33 for any thin film. The high values can be attributed to optimized deposition conditions and the low stress measured for the thin film arrangement on the substrate. The technique has been verified by obtaining a null response for silicon dioxide and by measuring d33 values of similar magnitude for PSZT thin films using an atomic force microscope in the same testing arrangement. The piezoelectric response has been mapped to study variations across the thin film and with distance from the top electrode.

The effect of post-deposition cooling rate on the orientation of piezoelectric (Pb0.92Sr0.08)(Zr0.65Ti0.35)O3 thin films deposited by RF magnetron sputtering

Strontium-doped lead zirconate titanate (PSZT) has been reported for its high piezoelectric and ferroelectric properties. The deposition of piezoelectric thin films (from a few nanometres to a few microns) is an essential part of microsystem devices for sensing and actuating. For PSZT to exhibit pronounced piezoelectric behaviour it must have a crystalline grain structure (perovskite orientation). This paper is a study of the deposition of PSZT thin films by RF magnetron sputtering and the effect of cooling rate, after deposition at temperatures between 500 °C and 700 °C. X-ray diffraction (XRD) results are used to show how a cooling rate of 5 °C min−1 increases the degree of perovskite orientation in sputtered films, when compared to a cooling rate of 15 °C min−1. X-ray photoelectron spectroscopy and energy dispersive x-ray analyses were used to determine the composition of the thin films. Results from deposition on silicon membranes and the position of diffraction peak patterns in XRD results are used to demonstrate low stress in the deposited films. Atomic force microscope imaging is used to show the crystalline nature of the PSZT thin films.

Orientation Dependence of Strontium-doped Lead Zirconate Titanate (PSZT) Thin Films on RF Magnetron Sputtering Conditions

ABSTRACTStudies on strontium-doped lead zirconate titanate (PSZT) have been reported for its high piezoelectric and ferroelectric properties. For PSZT to exhibit pronounced piezoelectric behaviour it must have a crystalline grain structure (perovskite orientation). This paper is a study of the deposition of PSZT thin films by RF magnetron sputtering and the effect of cooling rate, after deposition at temperatures between 500 °C and 700 °C. X-Ray Diffraction (XRD) results are used to show how a cooling rate of 5 °C/min increases the degree of perovskite orientation in sputtered films, when compared to a cooling rate of 15 °C/min. The absence of significant shifts in the positions of diffraction peak patterns in XRD results are used to demonstrate low stress in the deposited films. Atomic Force Microscope (AFM) imaging is used to show the crystalline nature of the PSZT thin films.