Polymer composites that are suitable for use as electromagnetic interference mitigaters include a lossy polymeric matrix, ceramic particles dispersed within the polymeric matrix, and conductive particles dispersed within the polymeric matrix. The lossy polymeric matrix may be a fluorocarbon-based polymer matrix, or an epoxy-based polymer matrix. The ceramic particles may be metal oxide particles, especially copper oxide (CuO) particles. The conductive particles may be carbon black. Other electromagnetic interference mitigating polymer matrices include a lossy polymeric matrix and copper oxide (CuO) particles dispersed within the polymeric matrix.