Development of new solution method using citric acid and ethylenediamine for borate compounds

Abstract

A new solution method that can be used to synthesize borate compounds was developed using citric acid and ethylenediamine. The conventional polymerizable complex method (polyester method) has a significant advantage in terms of homogeneity of the precursor, and it has been utilized in the synthesis of numerous oxide ceramics. However, it is very difficult to synthesize borate compounds by the conventional polymerizable complex method because boron reacts with the glycol that is necessary for the polymerization as polyester and is volatilized from the solution. In this paper, functional borate compounds such as YBO3:Eu3+, InBO3, and K3Ta3B2O12 were synthesized by the conventional polyester-type polymerizable complex method as well as the new solution method. In the polyester method, citric acid was dissolved in propylene glycol and the component metal salts were then dissolved in this solution. In the method that we propose in this paper, citric acid and ethylenediamine were dissolved in distilled water, and component metal salts were added to the solution. All solutions were heated at 403 K with stirring for the polymerization reaction to proceed, yielding polymer resins. The resins were heated to 723 K and powder precursors were obtained. The precursors were calcinated under various temperature conditions. In the case of YBO3:Eu3+, the formed product was Y2O3 by the polyester method due to volatilization of boron. On the other hand, single-phase YBO3:Eu3+ was synthesized by the new method. YBO3:Eu3+ synthesized by the method showed higher photoluminescence intensity than samples synthesized by a solid-state reaction method and the complex gelation method. Synthesis of single phase InBO3 and K3Ta3B2O12 was also successfully demonstrated by the method using a very small excess amount of H3BO3.