Ceramics, sintered lead zirconate titanate

S. Venkataramani, Calcining and Its Effects on Sintering and Properties of Lead Zirconate Titanate Ceramics, Ph.D. thesis, Pennsylvania State University, 1981. 

Pressure sintering techniques have also been used to fabricate transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics in air and in oxygen-gas atmosphere [31]. The microstructure of the sintered body was not uniform it was completely dense near the surface, but it was porous at the center. The thickness of the dense layer increased with sintering time and oxygen-gas pressure in the sintering atmosphere. Vaporization of PbO from the specimen surface and resultant formation of lattice vacancies were attributed to this microstructural evolution. Diffusion of the gas trapped in the pores was also important in determining the thickness of the dense layer. When the PLZT specimen was sintered in air at 1200 °C for 8 h, the thickness of the dense layer was 0.25 mm. Therefore, if the specimen thickness was 0.5 mm, the whole specimen was dense and transparent. When the specimen was sintered in an oxygen-gas atmosphere under the same conditions, the specimen thickness increased markedly. 

A special class of materials that is also ferroelectric are electrooptic ceramics. Materials such as lanthanum-modified lead zirconate titanate (PLZT) produce excellent electrooptic devices. These polycrystalline ceramics exhibit voltage-variable behavior—that is, they can be switched from optically transparent to opaque by the application of voltage. Most of these devices, which are used for shutters, modulators, and displays, are processed by hot pressing to full density. Experiments in many laboratories are being carried out to tape-cast these materials into thin sheets. The main problem encountered to date has been the ability to sinter to full density. The use of nanosized powders has helped in this regard. The ability to tape-cast large sheets could open a wide variety of applications for these materials. 

Abe Y, Kakegawa K (2002) Fabrication of optically transparent lead lanthanum zirconate titanate ((Pb, La)(Zr, Ti)03) ceramics by a three-stage-atmospheie-sintering technique. J Am Ceram Soc 85 473-475... 

Zhou LJ, Zhao Z, Zimmermann A, Aldinger F, Nygren M (2004) Preparation and properties of lead zirconate stannate titanate sintered by spark plasma sintering. J Am Ceram Soc 87 606-611... 

---