Cecil E. Land

Recent improvements in the optical and electrooptic properties of plzt ceramics

Continuing studies on the improvement of the optical quality of lanthanum modified lead zirconate titanate (PLZT) ceramics have shown that (1) bulk residual porosity and (2) chemical inhomogeneity are primary factors contributing to optical losses in thick plates of the material. This paper describes methods by which both of these major faults in the ceramic can be virtually eliminated. In addition, the optical and electrooptic properties of the improved material are presented and compared with those of previously available materials. Successful methods of eliminating residual porosity and enhancing chemical homogeneity resulted from studies which led to improved hot-pressing techniques and chemical preparation of the PLZT powders. Essentially all of the residual porosity was eliminated by introducing an oxygen atmosphere during the hot-pressing process. Chemical homogeneity was improved significantly by using high purity liquid solutions for preparing the PLZT powders. A combination of lead oxide and sol...

A review of the effects of ion implantation on the photoferroelectric properties of PLZT ceramics

An intrinsic photoferroelectric effect can be used to store high quality photographic images in transparent, ferroelectric-phase lead lanthanum zirconate titanate (PLZT) ceramics. The intrinsic (near-UV) photo-sensitivity of this photoferroelectric image storage process is increased by about four orders of magnitude by coimplanting Ar, Ne and He ions into the surface exposed to image light. Coimplanting Al or Cr and Ne greatly improves the extrinsic (visible-light) photosensitivity and produces a relatively flat photo-response from 400 to 600 nm. This paper summarizes our present knowledge of the photoferroelectric image storage mechanism and reviews the effects of ion implantation with respect to photosensitivity enhancement.

Photoferroelectric effects in PLZT ceramics

A photoferroelectric effect described as photoassisted domain switching (PDS) is used to store high resolution, high contrast, nonvolatile optical information, including gray scale images in PLZT ceramics. Image storage is achieved by switching the ferroelectric remanent polarization while exposing the image on one of the indium tin oxide electroded surfaces of a PLZT plate, using near-UV light at the PLZT band gap energy (3.35 eV). PDS eliminates the photoconductive films required in previous PLZT image storage devices. Some characteristics of the PDS effect which apply to image storage and selective erasure are described. Image processing to achieve contrast enhancement is also discussed.

Variable birefringence, light scattering, and surface-deformation effects in PLZT ceramics

Abstract Electrooptic effects in PLZT ceramics are being considered for a number of device applications including spectral and variable density filters, light shutters, page composers for holographic memories, information and image storage devices, and various types of displays. This paper describes the several electrooptic effects briefly and discusses recent work which contributes to a better understanding of the effects.

Preparation and characterization of chemically derived (Pb,La)TiO/sub 3/ thin films

Ferroelectric lead lanthanum titanate (PLT) thin films with composition varying from pure PbTiO/sub 3/ to PLT 25/100 (0 to 25 mol.% La) were prepared by spin-casting 0.25M solutions containing metallo-organic precursors of Pb, La, and Ti. The dielectric and ferroelectric properties of the thin (410-nm) films were characterized. The dielectric constants of the films varied from approximately 80 to approximately 690 for La contents varying from 0 to 25 mol%, respectively. Dissipation factors varied from approximately 0.03 to approximately 0.09 over the same compositional range. The temperature dependence of the dielectric properties was also studied to determine the effects of La content on the Curie point (T/sub c/). As expected, T/sub c/ was found to decrease with increasing La concentration. Coercive field and remanent polarization also decreased with increased La concentration.<<ETX>>

Photoferroelectric image storage in antiferroelectric-phase PLZT ceramics

A recently discovered photoferroelectric (PFE) effect in which the electric-field-induced antiferroelectric (AFE)-to-ferroelectric (FE) phase transition is photoinhibited is used to store nonvolatile gray-scale images in lead lanthanum zirconate titanate (PLZT) ceramics. Stored images exhibit exceptionally high contrast and approximately linear gray-scale reproduction. Images are stored as spatial variations of the volume ratio of FE phase to the initial AFE phase. Localized variations of the ratio of FE to AFE phase produce related variations in light scattering. In the materials studied, the scattering effect partially depolarizes transmitted visible light, and the stored image can be viewed directly or projected onto a screen using crossed linear polarizers.

Electrooptic effects in ferroelectric ceramics

Ferroelectric ceramics are piezoelectric and optically birefringent. Moreover, their coefficients of piezoelectricity and birefringence are electrically variable. Consequently, these ceramics are applicable to a variety of devices: electrically tuned oscillators and transformers; miniaturized high-Q, high-frequency filters; FM discriminators; optical memories; electrically Controlled light shutters and valves; and electrically activated multicolor displays. This article deals with some possibilities for devices that exploit the electrically controllable optical effects. A later article will consider piezoelectric applications.

The effects of ion implantation on the photoferroelectric properties of lead lanthanum zirconate titanate ceramics

Abstract Earlier studies of Ar-, Ar + Ne- and Ar + Ne + He- implanted ferroelectric-phase lead lanthanum zirconate titanate (PLZT) ceramics indicate that ion implantation can increase the intrinsic (near-uv) photoferroelectric sensitivity by more than four orders of magnitude compared to that of unimplanted PLZT. More recent studies involving implantation of chemically active ions, e.g., Al and Cr, indicate that the absorption spectrum of the implanted region can be extended from the near-uv to the visible, and that the extrinsic (visible-light) photoferroelectric sensitivity can be improved substantially with respect to that of PLZT implanted with inert ions. The results of these studies are reviewed and photographic sensitivities of Ar-, Ar + Ne-, Ar + Ne + He-, Al-, Cr-, Fe-, and Fe + Ne- implanted PLZT at both near-uv and visible-light wavelengths are compared with the sensitivities of other image storage media.

Photoinduced currents in PZT thin films.

The photoinduced currents in a 0.5-microm thick PZT films have been measured as a function of wavelength and poling direction for films on a platinum base electrode and with either aluminum or gold semitransparent top electrodes. Photocurrents display an Urbachlike, exponential dependence on photon energy with additional features relating to interference effects within the film. Transport of the photoexcited carriers is dominated by traps, resulting in a small overall collection efficiency.

Photoferroelectric sensitivity enhancement in PLZT by thermal diffusion of metals

Abstract We reported in previous papers that both the near-UV and visible photosensitivities of PLZT ceramic can be greatly enhanced by ion implantation. We present new results which suggest that a combination of thermal diffusion of Al and implantation of Ne produces photosensitivity enhancement greater than that achieved with ion implantation alone.