Study of the Phase Formation Processes and Their Influence on the Change in the Optical and Shielding Characteristics of 0.25ZnO–0.25Al2O3–0.25WO3–0.25Bi2O3 Ceramics

Abstract

The phase formation processes in 0.25ZnO–0.25Al2O3–0.25WO3–0.25Bi2O3 ceramics with variation in the thermal annealing temperature were evaluated in this study. According to the obtained data on the phase composition dependent on the annealing temperature, the phase transformation dynamics, which can be written in the form of ZnO/Bi2O3/WO3/Al2O3 → ZnBi38O60/ZnO/Bi2WO6/WO3 → Bi2Al4O9/ZnBi38O60/Bi2WO6/ZnO/WO3 → ZnWO4/Bi2WO6/ZnAl2O4/ZnO → ZnWO4/Bi2WO6/ZnAl2O4 → Bi2WO6/ZnWO4/ZnAl2O4 → ZnAl2O4/Bi2WO6/Bi2W2O9, were established. It has been found that the formation of phases of complex oxides of the ZnWO4, Bi2WO6 and Bi2W2O9 types in the composition of ceramics leads to an increase in the density of ceramics up to 8.05–8.10 g/cm3, which positively affects the shielding efficiency and strength characteristics. According to the data on the change in strength characteristics, it was found that a change in the density of ceramics from 6.3 to 8.05–8.10 g/cm3 leads to strengthening and an increase in the crack resistance of ceramics by 75–80%, which indicates a high strength of ceramics and their increased resistance to external influences. As shown by the evaluation of the shielding characteristics, an increase in the density of ceramics due to a phase composition change leads to an increase in the shielding efficiency and a decrease in gamma intensity by a factor of 3–3.5. At the same time, on the base of the data presented, it can be concluded that ceramics obtained in the range of 900–1100 °C have both high shielding characteristics and high strength and resistance to external influences.