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

Abstract

Transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics were fabricated by air-pressure sintering. When the PLZT (9/65/35) specimens were sintered in air, the microstructure was not uniform throughout the body; the outer region near the surface was completely dense, while the inner region of the body was porous. The thickness of the outer dense layer increased parabolically with sintering time. When the specimen was sintered in air at 1200°C for 8 h, the thickness of the dense layer was ϳ0.25 mm. Therefore, when the specimen had a thickness of <0.5 mm, it was dense and transparent. This difference in microstructure was attributed to the formation of lattice vacancies as a result of PbO evaporation from the surface. The sintering atmosphere also was important in determining the thickness of the dense layer. The thickness was strongly dependent on the oxygen partial pressure of the atmosphere. The oxygen-gas trapped in pores was deemed to migrate easily through the lattice vacancies. By sintering in an oxygen-gas atmosphere at 1200°C for 8 h, a transparent PLZT with thickness up to 2 mm was fabricated.

Progress in synthesis of ferroelectric ceramic materials via high-energy mechanochemical technique

“…Optical transparency of a transparent PLZT ceramic is determined by both the concentration of lanthanum and the ratio of Zr/Ti, with a maximum in transparency occurring along the FE-PE phase boundary and beyond [1,[84][85][86][87][88][89][90][91][92][93][94][95][96]. Four types of electro-optic effects have been found to be operative in transparent ferroelectric ceramics.…”

“…PLZT8/65/36 is a typical relaxor ferroelectric material having high dielectric constant and low coercive field. It can be sintered to transparent ceramics that is a novel electro-optic material and can be used for a variety of applications such as electro-optic switches [84][85][86][87][88][89][90][91][92][93]. PLZT7/60/40 possesses the highest values of piezoelectric longitudinal coefficient (d 33 = 710 pC/N) and electromechanical planar coupling (k p = 0.72) among the available PLZT ceramics ever reported in the literature [93].…”

Optical and electro-optical characteristics of hot-pressing (Pb_1-xLa_x)TiO₃ ferroelectric ceramics

“…A general characteristic of all the compositions of PLT studied here is the decrease of the conductivity with the sequence of thermal treatments, suggesting possible excess of PbO in the grain boundaries that would be eliminated during the thermal treatments (18). It is generally believed that trivalent La +3 ions replace for Pb +2 ions, requiring a charge compensation process in the PT-based perovskite lattice.…”

Reaction sintering of lead zinc niobate–lead zirconate titanate ceramics

“…22 These phenomena have been also observed in other systems. For example, the evaporation of PbO in PZT 22,25 or lead lanthanum zirconate titanate (PLZT) 23,24 generates oxygen and lead vacancies to a certain degree, thereby enhancing the transport of material and the process of densification that occur during the sintering process. In the present system, however, the evaporation of PbO was not one of the main factors, because it was identical for all the specimens.…”