Phase transitions in calcium phosphates

This project has received funding from the Research Council of Lithuania (LMTLT), agreement No S-MIP-23-85.

Abstract:

Calcium phosphates (CPs) are a family of materials widely used in many areas, including medicine and bone regeneration, catalysis, as host matrices for the development of optical materials, etc. CPs can be classified by many parameters, including crystal structure, Ca-to-P ratio, presence of other structural species. Whereas some CPs can be easily synthesized by precipitation from aqueous solutions or solid-state reaction, some phases can be obtained only through the phase transformation processes from less stable CPs. An outstanding member of the CP family is amorphous CP (ACP), which can be used as a precursor for synthesizing other phosphate-based materials. Partial substitution of Ca by other ions allows the combination biocompatibility of CPs with substitution-induced properties, resulting in the application of these materials in new areas such as various imaging modalities, including fluorescence, magnetic resonance, or multimodal imaging. Moreover, Ln-doped phosphates are essential materials in the area of optical thermometry and solid-state lightning. The main objective of this project is to investigate the phase transformations of pristine and Ln-substituted ACP in molten salts and aqueous media. The project will focus on two primary ways to create new structural states. The first one involves the phase transformations of pristine and Ln-substituted ACP in different molten salts. This approach will provide new insights into the phase transformations in CPs and fundamental aspects of crystal growth. Moreover, this approach will allow the synthesis of Ln-substituted CPs with tunable optical properties caused by the self-reduction of redox-active Ln ions. The second – phase conversion of ACPs in aqueous medium in the presence of foreign ions. This part will allow determining the influence of foreign ions on the crystal growth of CPs and will lead to the formation of Ln-substituted CPs of a particular morphology or a complete transformation to Ln phosphates.

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