The influence of mechanochemical treatment of the Bi₂O₃–ZrO₂ system on the structural and dielectric properties of the sintered ceramics

Abstract

A powder mixture of α-Bi₂O₃ and ZrO₂, both monoclinic, in the molar ratio 2 : 3, was mechanochemically treated in a planetary ball mill in an air atmosphere for up to 20 h, using steel vial and hardened-steel balls as the milling medium. Mechanochemical reaction leads to the gradual formation of an amorphous phase. After 5 h of milling the starting α-Bi₂O₃ and ZrO₂ were transformed fully into a non-crystalline phase. After milling for various times the powders were compacted by pressing and isothermal sintering. The pressed and sintered densities depended on the milling time. Depending on the duration of the mechanochemical treatment and sintering temperature, the phases: γ-Bi₁₂(Zr _x Fe_1−x )O₂₀; Bi(Zr _x Fe_1−x )O₃ and Bi₂(Zr _x Fe_1−x )₄O₉ were obtained by reactive sintering, whereby the Fe originates from vial and ball debris. The dielectric permittivity of the sintered samples significantly depends on the milling time. Samples milled for 10 and 15 h and subsequently sintered at 800 °C for 24 h exhibit a hysteresis dependence of the dielectric shift (in altering electric fields higher than 10 kV/cm at room temperature), confirming that the synthesized materials possess ferroelectric properties.