Mesoporous hydroxyapatite (HA) materials demonstrate advantages as catalysts and as support systems for catalysis, as adsorbent materials for removing contamination from soil and water, and as nanocarriers of functional agents for bone-related therapies. The present research demonstrates the possibility of the enlargement of the Brunauer–Emmett–Teller specific surface area (SSA), pore volume, and average pore diameter via changing the synthesis medium and ripening the material in the mother solution after the precipitation processes have been completed. HA powders were investigated via chemical analysis, X-ray diffraction analysis, Fourier-transform IR spectroscopy, transmission electron microscopy (TEM), and scanning (SEM) electron microscopy. Their SSA, pore volume, and pore-size distributions were determined via low-temperature nitrogen adsorption measurements, the zeta potential was established, and electron paramagnetic resonance (EPR) spectroscopy was performed. When the materials were synthesized in water–ethanol and water–acetone media, the SSA and total pore volume were 52.1 m²g⁻¹ and 116.4 m²g⁻¹, and 0.231 and 0.286 cm³g⁻¹, respectively. After ripening for 21 days, the particle morphology changed, the length/width aspect ratio decreased, and looser and smaller powder agglomerates were obtained. These changes in their characteristics led to an increase in SSA for the water and water–ethanol samples, while pore volume demonstrated a multiplied increase for all samples, reaching 0.593 cm³g⁻¹ for the water–acetone sample.

Powders based on β-tricalcium phosphate (β-TCP) containing sulphate groups at up to 12.0 mol.% were synthesised by chemical precipitation from aqueous solutions. The obtained materials were characterised by X-ray phase analysis, Fourier transform infrared spectroscopy, measurement of specific surface area, scanning electron microscopy, energy dispersive analysis, synchronous thermal analysis, mass spectra investigations and biological assays. It was established that during the synthesis, the obtained materials lose the sulphate groups in the course of heat treatment at 900 or 1200 °C. These groups stabilise low-temperature β-TCP, but when introduced at a high concentration, the sulphate groups contribute to the formation of hydroxyapatite during the heat treatment. Specific surface area of the powders proved to be in the range 81.7–96.5 m²/g. Results of biological assays showed cytocompatibility of both pure β-TCP and samples of sulphate-containing β-TCP. Additionally, matrix properties in the culture of MG-63 cells were revealed in all samples. Thus, the obtained materials are promising for biomedical applications.

Zirconia-toughened alumina (ZTA) powders with 20.0 wt.% of ZrO₂ were synthesized using the coprecipitation method. Transmission electron microscopy indicated that the powders contained needle-like particles 15–30 nm long and 50–70 nm flake-like particles with a uniform component distribution. Effects of different Y₂O₃ concentrations (3.0, 4.0, or 5.0 mol.%) and 0.5 wt.% of MnO on the phase composition, microstructure, and physicomechanical properties of the composites were evaluated after sintering at 1600 °C. The microhardness of 5ZTA-Mn samples (5.0 mol.% of Y₂O₃ and 0.5 wt.% of MnO) was 1653 ± 50 HV when density reached 4.18 g/cm³. For digital light processing on a commercial 3D printer Anycubic Photon S, acrylate-based homogeneous slurries were obtained. Compositions based on ZTA powder stabilized with 5.0 mol.% of Y₂O₃ and containing 0.5 wt.% of MnO were studied. MnO in the materials improved polymerization depth during the UV-curing process as compared to 5ZTA materials. The microstructure and mechanical properties of the 5ZTA-Mn composites were investigated at the sintering temperature of 1600 °C. Compared with 5ZTA, the 5ZTA-Mn composites showed higher density (4.0 g/cm³) and microhardness (1409 ± 50 HV). According to in vitro experiments, the newly developed materials are promising for biomedical applications and can serve as a basis for the production of personalized implants via digital light processing printing.

In this article, we have studied the influence of Mn²⁺ on the properties (phase composition, porosity, microstructure, three-point bending strength, and microhardness) and sintering of the ZrO₂–Al₂O₃–SiO₂ composite ceramic materials. The ZrO₂–Al₂O₃–SiO₂ ceramic powder containing 2.5 wt % Al₂O₃ and 0.5 wt % SiO₂ with specific area of 24.7 m²/g is synthesized through the coprecipitation method. Three concentrations of Mn²⁺ are considered: 0.25, 0.50, and 0.75 mol %. The introduction of Mn²⁺ leads to a significant increase in mechanical properties. The samples are sintered at 1250 and 1300°C for 2 h. The highest value of strength at three-point bending of 761 ± 36 MPa and microhardness of 9.5 ± 0.5 GPa is demonstrated by the material of the composition ZrO₂–Al₂O₃–SiO₂ containing 0.75 mol % Mn²⁺ sintered at 1300°С. The crack resistance of this material is 7.0 MPa m^1/2. At the same time, the highest values of crack resistance of 9.3 ± 0.5 MPa m^1/2 are shown by materials of the ZrO₂–Al₂O₃–SiO₂ composition containing 0.75 mol % Mn²⁺ sintered at 1250°C.

Calcium sulfate (CS) materials containing terbium ions at 0, 1.0, or 2.0 mol.% were obtained by mechanochemical synthesis. According to X-ray diffraction data, the powder materials are characterized by the presence of a CaSO4×0.5H2O phase, while Tb3+ is incorporated into the lattice at ≤1.0 mol.%. Specific surface area enlarged from 2.1 to 22.5 m2/g as crystallite size decreased from 68 to 31 nm and the Tb3+ concentration increased up to 1.0 mol.%. Thermal analysis showed that terbium slightly raises the temperature of CaSO4×2H2O-to-CaSO4 transition. The presence of Tb3+ did not affect the solubility of the CS cements. Furthermore, after 7 days of soaking of the materials in a simulated body fluid, a calcium phosphate layer formed corresponding to a hydroxyapatite phase, in contrast to the pure cements. Luminescent properties were studied by excitation at 276 nm. The recorded emission peaks of the CS materials indicated that the luminescence of the samples is green and blue, with the most intense luminescence observed for samples containing 1.0 mol.% Tb3+. The developed materials can find applications in medicine as bioimplants for the regeneration and restoration of bone tissue with a possibility of noninvasive monitoring of the bone restoration process.