Synthesis of h-BN encapsulated spherical core–shell structured SiO2@Sr2Si5N8:Eu2+ red phosphors

A facile method was designed for the successful synthesis of highly stable spherical (oxo)nitridosilicate phosphors with excellent monodispersity, high coating density and improved luminescent properties. The novel h-BN-encapsulated spherical core–shell SiO2@Sr2Si5N8:Eu2+ red-emitting phosphors were successfully synthesized by an interfacial reaction mechanism followed by a subsequent gas reduction and nitridation process. A thin film of hexagonal boron nitride (h-BN) was formed in situ during the synthesis process, leading to core–shell SiO2@Sr2Si5N8:Eu2+ phosphors with a perfectly spherical shape, narrow size distribution, non-agglomeration and a smooth surface. The particles consist of three layers: the outer h-BN film; the middle Sr2Si5N8:Eu2+ phosphor shell and the amorphous SiO2 core. Under UV and blue light excitation, the SiO2@Sr2Si5N8:Eu2+ phosphors show intense red emission due to the 4f65d–4f7 transition of the Eu2+ ions. Furthermore, this method is superior to the traditional gas reduction and nitridation method because of the lower temperature at which synthesis occurs.