Current research on zirconia toughened alumina (ZTA) systems employed in total hip joint replacement applications is focused on the usage of alternative stabilizers to improve their properties. Herein, a wide range of dysprosium (Dy3+) additions to ZTA systems have been formed through an in situ method. Dy3+ induced significant structural changes in ZrO2 rather than the α-Al2O3 component of the composite. Dy3+ tends to occupy along the a = b-axis of the ZrO2 lattice to stabilize tetragonal zirconia (t-ZrO2), whereas its enhanced accumulation directed the formation of cubic zirconia (c-ZrO2). As a consequence of phase transition, a different behavior in the emission characteristics was also noticed. However, t- → c-ZrO2 phase transition was not found to affect the paramagnetic behavior of Dy3+ added ZTA systems. The structural stability of the Dy3+ added ZTA systems was preserved until 1500 °C, and moreover it was also determined that optimum Dy3+ content is essential for enhanced mechanical stability of the composite.

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The concomitant effects of adding varied amounts of TiO2 and temperature of heat treatment on the crystallization of ZrSiO4 from SiO2–ZrO2 binary systems were investigated. The results showed that the t-ZrO2 phase is stabilized in the amorphous SiO2 network, and the simultaneous occurrence of SiO2 crystallization along with the tetragonal zirconia (t-ZrO2) → monoclinic zirconia (m-ZrO2) phase transition tends to activate the reaction between m-ZrO2 and SiO2 to yield ZrSiO4 at elevated temperatures. The formation of metastable ZrTiO4 is also witnessed in the intermediate temperatures that were dependent on TiO2 content, and its dissociation into their individual ZrO2 and TiO2 oxides resulted in ZrSiO4 formation. The Ti4+ occupancy at the Zr4+ lattice sites ensured enhanced crystallization of ZrSiO4, and the limit of Ti4+ occupancy is determined as 9%. Excess TiO2 discarded from the ZrSiO4 lattice gets crystallized into rutile TiO2 (r-TiO2).

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A series of Gd dopings in zirconia-toughened alumina (ZTA) systems were undertaken to explore the resultant structural, morphological, hydrothermal aging, and mechanical behavior and imaging contrast abilities. The results from the characterization techniques demonstrate the significance of Gd in preserving the structural stability of ZTA systems. ZTA undergoes phase degradation with 10 wt % Gd at 1400 °C, while the 100 wt % Gd yields GdAlO even at 1200 °C. Gd doping at the intermediate level preserves the structural stability of ZTA systems until 1400 °C. Gd occupies the ZrO lattice, and its gradual accumulation induces tetragonal ZrO (t-ZrO) to cubic ZrO (c-ZrO) phase transition. α-AlO crystallizes at 1200 °C and remains unperturbed except for its reaction with the free Gd ions to yield GdAlO. Aging studies and mechanical tests signify the impeccable role of Gd in ZTA systems to resist phase degradation. Further, the imaging contrast ability of ZTA systems due to Gd doping is verified from the in vitro magnetic resonance imaging (MRI) tests.

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