The present invention relates to a bi-directional broadcasting system for a small space. The method provides polymeric organic iridium compositions comprising at least one cyclometallated ligand and at least one ketopyrrole ligand. The impurities are sealed inside the fly ash 11 not to transfer to the outside so that the surface of the fly ash is covered up with a ceramic shell 13 to form the ceramic foam 10 having two layers in and out.