Search

The electromechanical properties of sol-gel derived ferroelectric Pb(Zro.53Tio.47)O3 (PZT 53/47) thin layers deposited on silicon were determined as a function of fieldstrength, measurement frequency and total thickness. Both electrically-induced strains (e) and piezoelectric properties (d33) were characterized by interferometry. Dielectric spectroscopy and polarization switching (P-E) measurements were determined for comparative purposes. An asymmetry between forward and the reverse bias conditions in the e-E displacements was found for both 5-layer deposited and 9-layer deposited structures. However, no asymmetry was observed in the P-E hysteresis characteristics. In addition, the electrically-induced strains and the piezoelectric response were found to be dependent on measurement frequency. No significant frequency dependence was observed in the polarization or dielectric responses. The results are discussed in terms of a possible clamping effect for polarization switching.

The electromechanical properties of sol-gel-derived ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT 53/47) thin layers deposited on silicon were determined as a function of field strength, measurement frequency, and total thickness. Both electrically induced strains (∊) and piezoelectric properties (d33) were characterized by interferometry. Dielectric spectroscopy and polarization switching (P-E) measurements were determined for comparative purposes. An asymmetry between forward and the reverse bias conditions in the ∊-E displacements was found for both five-layer deposited and nine-layer deposited structures. However, no asymmetry was observed in the P-E hysteresis characteristics. In addition, the electrically induced strains and the piezoelectric response were found to be dependent on measurement frequency. No significant frequency dependence was observed in the polarization or dielectric responses. The results are discussed in terms of a possible clamping effect on polarization switching.

The properties of thin layer ferroelectrics appear to differ, sometimes considerably. from those of bulk ceramics of the same composition. Most notably, a broadening of the temperature dependent dielectric anomaly, an increase in the coercive field and a decrease in the remnant polarization are frequently reported. Recent advances in processing thin layers by chemical methods, and in sol-gel processing in particular, have resulted in the capability of fabricating thin layer fermelectrics in which variations in phase composition and microstructure can be. controlled and minimized. In this work. single phase perovskite thin layers of lead zirconate. titanate (PZT) with a composition near the morphotropic phase boundary (Zr/Ti = 53/47) were deposited onto platinized silicon substrates by spin-casting pre-hydrolyzed alkoxide solutions. Ferroelectric and dielectric properties are reported as a function of layer thickness and discussed in terms of an interface effect, series impedance model, and the ac...

The piezoelectric properties of ferroelectric and antiferroelectric thin layers were investigated by interferometry as a function of frequency and dc electric bias. Materials included: a ferroelectric lead zirconate titanate (PZT) with a Zr/Ti ratio of 53/47; a relaxor ferroelectric La‐modified PZT with a Zr/Ti ratio of 70/30 and a La content of 7.8 at. %; and antiferroelectric lead zirconate. The hysteretic behavior of the piezoelectric coefficient due to polarization reversal was also studied. The layers were prepared by a sol‐gel method, and were found to have properties similar to bulk ceramics. Significant strain levels could be achieved in the materials due to the relatively high electric strengths supported in thin‐layer form. Polarization was found to be completely switchable between forward and reverse directions; however, the strain levels generated by switching were found to be inequivalent. In addition, pronounced piezoelectric relaxations and strong piezoelectric losses were observed.

This paper reports on infrared spectroscopy that was used to monitor and characterize solutions used in the preparation of PZT 53/47 powders, dried gels, and thin layers deposited on platinized silicon substrates. It was found that careful control of the chemistry of the precursor solutions, in particular the control of the formation of esters and their elimination, resulted in reproducible solutions which could be used to prepare thin layers with superior properties. In addition, it was found that phase development and microstructure were related to the precursor chemistry. Single-phase perovskite layers with uniform microstructures resulted from ester-free solutions and were suitable for ferroelectric applications (P[sub r] [approximately] 22 [mu]C/cm[sup 2], E[sub c] [approximately] 80 kV/cm, K [approximately] 800, tan [delta] [approximately] 0.01).

The method of rapid thermal processing (RTP) has been suggested to be a means by which the formation of intermediary phases in sol-gel derived Pb(Zr,Ti)O/sub 3/ (PZT) thin layers can be suppressed before the crystallization of the desired perovskite phase. However, the dependence of densification and crystallization processes in sol-gel derived materials on thermal processing conditions such as heating rate, /spl alpha/, and firing temperature, T/sub f/, can lead to differences in the properties of otherwise identical materials prepared by different thermal profiles. In this paper, the effects of thermal processing conditions on the properties of PZT 53/47 (i.e., Zr:Ti=53:47) thin layers are reported. The evolution of structure after RTP was examined by diffuse reflectance FTIR spectroscopy, and electron microscopy. It was found that crystallization of the perovskite phase shifted to higher temperatures, and the shrinkage normal to the plane of the substrate decreased, with increasing heating rate.

The evolution of structure and chemical distribution in sol-gel derived Pb(Zr0.53T10.47)O3 thin layers was monitored by x-ray diffraction, analytical electron microscopy, and diffuse reflectance Fourier transform infrared spectroscopy. Electron microscopy confirmed the as-deposited coatings were amorphous with short-range order. Medium-range order developed on heat treatment, and chemical heterogeneity was observed at the nanoscale. The extent of compositional heterogeneity decreased with increasing temperature. Above 500 °C, the coatings crystallized into an intermediate phase which converted to the perovskite phase above 600 °C.