Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

► First derivatives of cyclic phosphazenes containing two metals in non-geminal positions. ► Electron beam writing of nanoparticles within an amorphous host and embedded nanoparticle formation in the solid state. ► Growth mechanism of twinned nanocrystals of WP2O7. ► Stabilizing role of P4O7 during crystallization of embedded nanoparticles in oxide host. ► Model of sintering-based recrystallization to explain embedded nanoparticle formation.