Transparent Lead Lanthanum Zirconate Titanate Ceramics Derived from Oxide Mixture Via a Repeated Annealing Process
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Lead lanthanum zirconate titanate (PLZT9/65/35) ceramics were prepared from their oxide mixture via reactive sintering without involving a calcination step. PLZT ceramics sintered at 1000 °C for 4 h possessed a grain size of 3–4 m, a dielectric constant of 3670, a dielectric loss of 0.033 at 1 kHz, and a remnant polarization of 5.7 C/cm2 and coercive field of 4.6 kV/cm, respectively. Transparent PLZT ceramics were obtained by annealing the sintered samples at 1125 °C for 6 h repeatedly for 4 times without using hot pressing or oxygen flow. The grain size of PLZT ceramics increased to 4–6 m, with dielectric constant of 5187 and dielectric loss (1 kHz) of 0.036, and remnant polarization of 11 C/cm2 and coercive field of 5.3 kV/cm. The transparent PLZT ceramics demonstrated a transmittance of 42% at a wavelength of 550 nm.
Lead lanthanum zirconate titanate (PLZT) ceramics are of significant interest due to their high optical transparency and electro-optical characteristics.1,3 Optical shutters, switches, memories, and displays are only a few of many potential applications for this family of materials.3 PLZT ceramics were conventionally prepared by a solid-state reaction process, which involves the preparation of the PLZT powders by solid-state reaction of mixed oxides at high temperature and subsequent milling, pelleting, and sintering. It is very complicated and time consuming.3 Chemical preparation methods have also been employed to prepare PLZT ceramics.4 –8 These chemical preparation methods are advantageous over the conventional solid-state reaction process because they can largely lower calcination and final sintering temperatures because of atomic or molecular scale mixing. However, preparation of PLZT ceramics by the chemical methods is no different from the conventional process in terms of the processing complexity. Furthermore, chemical processes usually involve raw materials, which are very expensive and extremely sensitive to moisture, heat, and light. Moisture-sensitive metal alkoxides must be manipulated in a dry box. Hydrolyzing a mixture of alkoxides that do not have relatively compatible hydrolysis reaction rates results in the preferential precipitation of a more reactive alkoxide. Preparation of PLZT powders from inorganic precursors, for example, nitrate or chloride, which are relatively inexpensive, requires repeated washing after precipitation, making the process still time consuming and low yielding. All these characteristics of the chemical preparation methods make them essentially similar to the conventional solid-state reaction process. J. Mater. Res., Vol. 17, No. 5, May 2002
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Reaction sintering is a promising fabrication technique for multicomponent ceramics, in which the reactions between constituent phases take place during the sintering process at high temperatures. It is advantageous over the other earlier mentioned methods because of its simple processing procedure and enhancement in densification process. Preparation of lead
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