Keith G. Brooks

Rapid thermal annealing of sol-gel derived lead zirconate titanate thin films

Sol‐gel derived ferroelectric thin films of lead zirconate titanate have been annealed through the rapid thermal annealing (RTA) technique to investigate the effect of various annealing temperature‐time combinations. Crystallization of the film into the perovskite phase required 10 s at 600 °C and a mere 1 s at 700 °C. Rapid thermally annealed films recorded weak‐field permittivities greater than 1000, dissipation losses of 0.02–0.05, maximum remanent polarization of 29 μC/cm2, and coercive field around 40 kV/cm. RTA films are distinguished by superior breakdown strengths, and morphologically smoother surfaces. The frequency dependent dielectric constants have been discussed in terms of a lumped circuit model.

Sol-gel processing of PbTiO 3 and Pb(Zr 0.52 Ti 0.48 )O 3 fibers

Homogeneous and stoichiometric PbTiO 3 and PbZr 0.52 Ti 0.48 O 3 gel fibers were drawn from viscous solutions prepared by sol-gel processing of alkoxide precursors. The fibrous gels on heating at 450 and 600 °C, respectively, formed the well-crystallized phases of PbTiO 3 and PbZr 0.52 Ti 0.48 O 3 . Fibers heat treated at 700 °C are a few centimeters long and 50 to 150 μm in diameter. PbZr 0.52 Ti 0.48 O 3 fibers subjected to heat treatment at 700 °C for 1 h consisted of fully dense submicron grains (0.15 to 0.2 μm). However, PbTiO 3 fibers under analogous conditions showed a few micropores with grains of ∼0.1 μm. Dielectric constants of these PbTiO 3 and PbZr 0.52 Ti 0.48 O 3 fibers were approximately 300 and 800, respectively.

Electric field forced phase switching in La‐modified lead zirconate titanate stannate thin films

Electric field forced antiferroelectric to ferroelectric phase switching has been demonstrated in thin films of Pb0.97La0.02(Zr,Ti,Sn)O3 perovskites for the first time. Several compositions in the tetragonal antiferroelectric phase field of this system were prepared in thin film form by a sol‐gel technique. Forward and reverse switching threshold fields of 27–103 kV/cm and 18–62 kV/cm, respectively, were determined from polarization‐electric field hysteresis and incremental capacitance data. Switching times as fast as 300 ns were recorded for one of the antiferroelectric compositions. An electric field induced longitudinal strain of 0.16% was measured for a film of composition (Pb0.97La0.02)(Zr0.60Ti0.10Sn0.30)O3 using a laser ultradilatometer. These films are candidate materials for high charge storage integrated capacitors and microelectromechanical devices requiring large nonlinear strain response.

Piezoelectric PZT tubes and fibers for passive vibrational damping

Passive vibrational damping was demonstrated in piezoelectric lead zirconate titanate (PZT) tubes incorporated into a hard epoxy matrix. For a poled tube, the coupling constant k/sub 33/, measured from the resonance frequency, was about 0.66. Sol-gel methods were used to fabricate piezoelectric fibers of Pb(Zr/sub 0.52/Ti/sub 0.48/)O/sub 3/ and niobium- and CdBO/sub 3/-substituted PZT. Continuous and fine gel fibers of about 5 to 100 mu m in diameter were prepared by extruding and drawing spinnable viscous resins through a spinnaret. When fired at 600 degrees C for 1 h, these fibers exhibited well-crystallized perovskite phases of PZT. Fibers fired between 700 degrees and 1250 degrees C were dense with varying grain sizes (0.1 to 5 mu m). The dielectric constant of Pb(Zr/sub 0.52/Ti/sub 0.48/)O/sub 3/ fiber that was fired at 700 degrees C for 1 h was about 800. These fibers will be incorporated into structural materials to obtain maximum damping properties.<<ETX>>

Ferroelectric Switching in Lead Zirconatelead Zinc Niobate Thin Films

Thin films of PbZrO 3 -Pb(Zn 0.33 Nb 0.67 )0 3 , with PZN contents of 8- 12%, were fabricated through the sol-gel spin-on technique. The structural, low frequency capacitive, and polarization reversal characteristics were investigated as a function of composition in this solid solution system. The switching of ferroelectric polarization was tested by a sequence of square wave pulses consisting of two positive pulses followed by two negative pulses. Compositions with higher PZN contents are promising for switching applications; the films were typically characterized by a switched charge of 4-14 μC/cm 2 , coercive field of around 30 kV/cm, and relative permittivity of 400-800.

Dielectric behavior of ferroelectric thin films at high frequencies

The high-frequency dielectric response of sol-gel-derived lead zirconate titanate (PZT) thin films have been investigated. Conceptualizing the presence of interface layers was critical in explaining the dielectric measurements. By a careful control of the processing parameters, aided by rapid thermal annealing, the low-frequency dielectric characteristics could be sustained up to a gigahertz range. Ba/sub 0.5/Sr/sub 0.5/TiO/sub 3/, which is paraelectric at room temperature, appears to be a potential candidate material for high-frequency applications.<<ETX>>

Properties of Pzt Thin Films with 2CdO·B2O3 Glass Phase Additive

Lead zirconate titanate thin films containing 0-4 wt.% of 2CdO·B 2 O 3 glass phase additive have been fabricated by sol-gel processing. Smooth dense perovskite films of approximately 3500A thickness were formed on Si wafers by a multiple layer spin coating process followed by rapid thermal annealing. Remanent polarizations of up to 23μC/cm 2 were measured. Hysteresis properties were found to be very sensitive to annealing time at 700°C, with remanence being maximized at 100-200 seconds.