Fabrication of Transparent Lead Lanthanum Zirconate Titanate Ceramics from Fine Powders by Two‐Stage Sintering

Abstract

Transparent lead lanthanum zirconate titanate (PLZT) ceramics were fabricated from fine powders using an inexpensive two-stage sintering technique. The powders were prepared by hydrolysis from low-cost inorganic precursors. In the two-stage sintering method, uniaxially pressed green pellets were densified to nearly theoretical values in an oxygen gas atmosphere during the first-stage sintering, at 1000°C for 1 h, and then residual, free lead oxide in the pellets was removed by second-stage sintering at 1100°C for 12 h. Transparent ceramic with an average grain size of 1.6 Fm and a porosity of 1.3% was obtained. The transparency and dielectric characteristics of the present samples were compared with those of hot-pressed samples: The study of the polarization-field hysteresis loops of the present samples yielded a remanent polarization of 6.8 FC/m2 and a coercive field of 1.6 kV/cm. The low coercive field of PLZT ceramics could potentially reduce the driving voltage of electrooptic devices in many applications.

Microstructural Evolution of Transparent PLZT Ceramics Sintered in Air and Oxygen Atmospheres

“…There are several reports showing that PbO vaporization is important in determining the final microstructure of lead-containing materials. 5,6,8,9 It previously has been observed that an excess of PbO in PZT ceramics expedites densification during the initial and intermediate stages of sintering. 9 However, excess PbO is detrimental to the final stage of sintering.…”

“…However, if the pores are filled with oxygen-gas, they disappear relatively easily by the migration of oxygen via lattice diffusion. 8 The volatilization of PbO starts from the specimen surface, so that a variation in microstructure is expected depending on location within the specimen.…”

“…5 Oxygen also is important in densification because of its great solubility and diffusivity in this system. 8,12 During the final stage of sintering, if the isolated pores are filled with inert gases, such as argon or nitrogen, the pores remain intact, and the pore size can increase by coalescence. However, if the pores are filled with oxygen-gas, they disappear relatively easily by the migration of oxygen via lattice diffusion.…”

“…1 To obtain transparent PLZT ceramics, the density of the body should be nearly 100% of its theoretical density, because even extremely low pore contents can scatter light, rendering the ceramic opaque. 2 Therefore, special techniques, such as hotpressing, 2 atmosphere-controlled liquid-phase sintering, [3][4][5][6][7][8] and vacuum sintering, 5,7 have been used to affect the complete removal of pores. However, these procedures are either not suitable for mass production or uneconomical because of the extended sintering time (usually Ͼ60 h) in an oxygen-gas atmosphere.…”

Effect of Manganese Ion Diffusion on the Microstructural Evolution of Lead Lanthanum Zirconate Titanate Ceramic

“…Thus, the sintering behavior of PLZT ceramic is important and has been widely investigated. [2][3][4] Recently, we observed that the microstructure of PLZT sintered in air was not homogeneous. 5 The outer regions of specimens were completely dense while the inner regions remianed porous after sintering in air at 1200°C for 8 h. The dense outer layer became thicker with increasing sintering time or oxygen partial pressure in the ambient gas.…”