Phase Stabilization of <scp> <scp>ZrO</scp> </scp> ₂ Polymorph by Combined Additions of <scp> <scp>Ca</scp> </scp> ²⁺ and <scp>PO</scp> ₄ ³⁻ Ions Through an <i>In Situ</i> Synthetic Approach

Abstract

This study has been aimed at the phase stabilization of tetragonal Zirconia ( t ‐ ZrO 2 ) by the additions of Ca 2+ and PO 4 3− through an in situ synthetic approach. A wide range of variations have been attempted in which the precursor concentrations of Ca 2+ and PO 4 3− have been maintained constant for every synthesis. The characterization results from XRD , Raman spectra, FT ‐ IR spectra, XRF , and the quantitative analysis have confirmed the t ‐ ZrO 2 stabilization for the selected concentrations ranging from 5% to 20% of Ca 2+ and PO 4 3− in the ZrO 2 system at 900°C. Pure ZrO 2 system without the additions of Ca 2+ and PO 4 3− have yielded the mixture of c ‐ ZrO 2 and m ‐ ZrO 2 at the investigated temperatures ranging between 800°C and 1000°C with no identified traces of t ‐ ZrO 2 . Thus, the stabilization of t ‐ ZrO 2 has been mainly attributed to the combined influence of Ca 2+ and PO 4 3− presence in the ZrO 2 matrix creating oxygen vacancies that has been confirmed from impedance measurements. Heat treatment beyond 900°C had resulted in the phase degradation leading to the formation of mixture of phases comprising of major amount of m ‐ ZrO 2 and minor amount of t ‐ ZrO 2 .