Probing the combined additions of Ca2+ and PO43− in the stabilized ZrO2 polymorph: structural, morphological and mechanical analysis

Abstract

In this study, we investigate the stabilization of discrete cubic zirconia (c-ZrO₂) polymorph in the presence of assorted range of Ca²⁺/PO₄³⁻ additions with constant 30 mol% of Y₂O₃ in all formulations. The combustion technique is used for the powder synthesis, and a set of analytical techniques are employed for comprehensive characterization. The combined limit of Ca²⁺/PO₄³⁻ to retain unique c-ZrO₂ is determined as 20 mol%. A further increment in Ca²⁺ and PO₄³⁻ additions confirms the crystallization of β-Ca₃(PO₄)₂ together with c-ZrO₂. The results indicate the accommodation of higher sized Ca²⁺ till 20 mol% in the already expanded c-ZrO₂ unit cell due to Y³⁺ occupancy, whereas PO₄³⁻ is dispersed in the ZrO₂ matrix in amorphous form. The indentation results indicate gradual increment in the mechanical properties of Ca²⁺-stabilized c-ZrO₂, and a sharp reduction is noticed in the mechanical data of c-ZrO₂, which possesses β-Ca₃(PO₄)₂ as a secondary phase.