A composite material is provided including a phosphor material of at least one of among hafnium oxide, niobium oxide, tantalum oxide or zirconium oxide as a conformal coating on a porous substrate, the composite characterized as exhibiting photoluminescence at room temperature. Also provided is a composite material including a phosphor material of at least one of among hafnium oxide, niobium oxide, tantalum oxide, zinc oxide or zirconium oxide as a conformal coating on a porous substrate, the composite characterized as exhibiting photoluminescence at room temperature and as having a broad emission spectrum having a width at 1/2 maximum greater than 80 nm.