Zinc phosphate as versatile material for potential biomedical applications Part 1.

Area of Science:

• Inorganic Chemistry
• Crystallography
• Materials Science

Background:

• Zinc phosphate tetrahydrates (ZPT) exist as different polymorphs with distinct crystallographic structures.
• Understanding the thermodynamic relationships and dehydration behavior of these polymorphs is crucial for their applications.

Purpose of the Study:

• To synthesize and characterize alpha- and beta-Hopeite, two polymorphs of ZPT.
• To investigate the thermodynamic interrelation and dehydration kinetics of these ZPT forms.
• To elucidate the role of hydrogen bonding in the structural and chemical properties of ZPT.

Main Methods:

• Hydrothermal crystallization for synthesis of ZPT polymorphs.
• X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), and Thermogravimetry-Mass Spectrometry (TGA-MS) for thermodynamic analysis.
• Low-temperature DRIFT, FT-Raman, and solid-state NMR ((1)H, (31)P MAS-NMR) for structural and bonding investigations.
• Heterogeneous step-reaction approach for dehydration kinetics studies.

Main Results:

• Successful synthesis of alpha- and beta-Hopeite via hydrothermal crystallization at different temperatures.
• Detailed thermodynamic interrelation and dehydration kinetics, including transition temperatures, were determined for both polymorphs.
• Structural analysis revealed oriented distortion of zinc phosphate tetrahedra due to specific hydrogen bonding patterns.

Conclusions:

• Alpha- and beta-Hopeite exhibit distinct crystallographic and thermodynamic properties influenced by hydrogen bonding.
• The study provides insights into the dehydration mechanisms and structural characteristics of ZPT polymorphs.
• Comparison with biogenic calcium phosphates highlights variations in chemical reactivity.