Optical Properties and Microstructure of Nanocrystalline Cubic Zirconia Prepared by High‐Pressure Spark Plasma Sintering

Abstract

The optical properties and microstructure are evaluated for a transparent cubic (8 mol% yttria-stabilized) zirconia (c-YSZ) prepared by high-pressure spark plasma sintering. Oxygen vacancies and residual pores are primary defects in the present transparent c-YSZ, and the combination influence of these two defects determines the optical properties. The as-sintered transparent zirconia strongly absorbs the incident light due to the formation of high concentration of oxygen vacancies. Annealing treatment in oxidizing atmosphere can improve the transparency by reducing oxygen defects. The existence of fine pores in the present zirconia causes scattering of the incident light.

Effect of sintering temperature on optical properties and microstructure of translucent zirconia prepared by high-pressure spark plasma sintering

“…The yellowish-brown appearance of c-YSZ is usually attributed to color centers (oxygen vacancies with trapped electrons) [9][10][11][12], [35][36][37], which are easily produced in c-YSZ under thermal reduction or electroreduction conditions [9][10][11][12], [35][36][37][38][39]. The SPS process provides both conditions: at high temperatures, vacuum and graphite dies yield a thermal reduction environment, and the applied current may also result in electroreduction.…”

“…These oxygen vacancies can cause strong light absorption through the association with free electrons to form color centers [9][10][11][12], [35][36][37], [39]. The oxygen vacancies with one trapped electron are F + centers and the ones with two trapped electrons are F centers.…”

“…Besides color centers, residual pores reduce transparency of c-YSZ, especially for the ultraviolet light (figures 2 and 3) [7,12,20], [39][40][41]. Figure 4 shows typical TEM microstructures of the as-sintered polycrystalline c-YSZ.…”

“…The absorption coefficient is reduced ( figure 6) because back-diffusion of oxygen reduces the concentration of color centers [10][11][12]. However, the color centers can coalesce and eventually develop into pores [12,36,39]. So the scattering coefficient is enhanced ( figure 7) owing to the increase of the porosity ( figure 5).…”

pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles

“…The doping of zirconia with Y 2 O 3 improves the thermal stability of the cubic form. The preparation of stable pure cubic zirconia at room temperature without any dopant has been extensively investigated [11][12][13]. Different methods have been explored to synthesize zirconia nanoparticles through various processes, such as hydrothermal precipitation [14,15], microwave-hydrothermal treatment [10], and sol-gel precipitation [3,[16][17][18].…”