Preparation of phosphate glasses via ethanol-based liquid-phase method

Abstract

Phosphate invert glasses (PIGs) are promising biomaterials because of their ability to release ions and their biocompatibility. Using water-based liquid-phase methods, PIGs can be synthesized at ambient temperature and pressure. However, the compositional range is limited owing to the hydrolysis of water-sensitive raw materials, such as NbCl₅ and TaCl₅, which produce insoluble hydroxides and oxides. Thus, the incorporation of tantalum (Ta) and niobium (Nb) into the PIG network structure is difficult, despite their ability to enhance chemical durability and introduce biological functionalities. In this work, an ethanol-based liquid-phase method was developed to prepare PIGs for certain water-sensitive raw materials. The ethanol content in the method is significantly related to the glass network structure and crystallization behavior. PIGs without crystalline phases were obtained with ethanol content up to 50 %, whereas higher ethanol content led to partial crystallization of K₂CaP₂O₇. Modifying the process can suppress crystallization at the high ethanol content, allowing the preparation of PIGs without crystalline phases. Thus, the proposed method can be used to prepare crystallization-free PIGs containing water-sensitive elements.