Gadolinium Doping in Zirconia-Toughened Alumina Systems and Their Structural, Mechanical, and Aging Behavior Repercussions.

A series of Gd3+ 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 Gd3+ in preserving the structural stability of ZTA systems. ZTA undergoes phase degradation with 10 wt % Gd3+ at 1400 °C, while the 100 wt % Gd3+ yields GdAlO3 even at 1200 °C. Gd3+ doping at the intermediate level preserves the structural stability of ZTA systems until 1400 °C. Gd3+ occupies the ZrO2 lattice, and its gradual accumulation induces tetragonal ZrO2 (t-ZrO2) to cubic ZrO2 (c-ZrO2) phase transition. α-Al2O3 crystallizes at 1200 °C and remains unperturbed except for its reaction with the free Gd3+ ions to yield GdAlO3. Aging studies and mechanical tests signify the impeccable role of Gd3+ in ZTA systems to resist phase degradation. Further, the imaging contrast ability of ZTA systems due to Gd3+ doping is verified from the in vitro magnetic resonance imaging (MRI) tests.

Structure, luminescence, mechanical and in vitro behavior of zirconia toughened alumina due to terbium substitutions.

The significance of Tb3+ inclusions at the zirconia toughened alumina (ZTA) structure was explored. The influence of Tb3+ content at the crystal structures of ZrO2 and Al2O3 and the resultant optical, mechanical, magnetic and cytotoxicity properties were deliberated. The critical role of Tb3+ to attain a structurally stable ZTA until 1500 °C is ensured. Depending on the Tb3+ content, either tetragonal zirconia (t-ZrO2) or cubic zirconia (c-ZrO2) structures were stabilized while the propensity of Tb3+ reaction with Al2O3 to yield TbAlO3 is transpired only after exceeding the occupancy limit in ZrO2. The green emission and paramagnetic features are imparted by the Tb3+ inclusions at the ZTA structure. Dense and pore free microstructures with a direct impact on the improved mechanical features of ZTA is empowered by the presence of Tb3+. Further, the results from MTT assay and live/dead cell staining ensured the negligence of Tb3+ contained ZTA systems to induce toxicity.

Structural and bio-mineralization features of alumina zirconia composite influenced by the combined Ca2+ and PO43- additions.

The structural and bioactivity features of alumina zirconia composite (AZC) due to Ca2+ and PO43- additions are demonstrated. An in situ synthetic approach, starting from the solution precursors is devised for the powder synthesis in which the assorted range of Ca2+ and PO43- additions were done to the equimolar concentrations of Al3+ and Zr4+ precursors. The results witnessed the unique crystallization of tetragonal zirconia (t-ZrO2) at 1100 °C while Ca2+, PO43- and Al2O3 remained in their amorphous state in the system. On further heat treatment, α-Al2O3 crystallized at 1200 °C, which enforced t- → m-ZrO2 transformation while Ca2+ and PO43- still retained their amorphous state. The immersion tests in simulated body fluid (SBF) solution validated the enhanced bio-mineralization activity of AZC due to Ca2+ and PO43- additions. The results from the indentation tests demonstrated good uniformity in the elastic modulus and hardness data of the investigated specimens. Further, in vitro cell culture tests ascertained the bioactivity of all the AZC compositions.