Porous shell/dense core structures prepared in tungsten phosphate glass through template-free route

The preparation of the 11.7Li2O–39.7WO3–10.9CaO–37.7P2O5 glass (pgLWCP) was based on a one-step heat treatment of the 6Li2O–18WO3–43CaO–33P2O5 (gLWCP) glass followed by leaching of the β-Ca2P2O7 phase formed during the crystallization process. The porous structure was formed in the region formerly occupied by the β-Ca2P2O7 phase. The gLWCP undergoes devitrification through surface crystallization. This process occurs after a thermal treatment in lower temperature and in a shorter period of time than that required for the complete crystallization. After acid leaching treatment, we obtained a core-/shell-like structure with a very well-defined dense glass (gLWCP)/porous glass (pgLWCP) interface. The pgLWCP exhibits reversible coloration–decoloration reactions.