Abstract: Calcined ceramic powder is made by blending a precursor powder with a form of carbon such as carbon black and heating the blend in an oxygenated atmosphere. The carbon acts as a separator, preventing coalescence of the percursor powder during the calcining process. The blend is characterized by the presence of interstitial spacing between the particles of the carbon powder and the precursor powder. The carbon is eventually oxidized to carbon dioxide and/or carbon monoxide and volatilizes as such, leaving behind the calcined ceramic powder. In a preferred embodiment, the heating is effected by microwave radiation. The carbon absorbs the microwave radiation, heating up the precursor powder and calcining it to form the ceramic powder. Once all the carbon has been oxidized, no more microwave radiation is absorbed, and the heating stops, making the process self-limiting.

Abstract: A composition which comprises a matrix polymer and, distributed therein, a particulate conductive filler. At least some of the filler particles are composed of a conductive polymer composition and/or the matrix comprises a sintered polymer. The matrix polymer and the filler particles and the method of distributing the particles are such that the particles maintain their identity in the matrix. For example, the particles are preferably highly cross-linked so that they have a hot modulus of at least 250 psi if the composition is prepared by melt extrusion or another process involving a high degree of shear; or a low-shear process such as sintering can be used. Preferably the matrix polymer is capable of coating the filler particles; for example, the matrix polymer and the filler polymer may be chemically similar. The invention is particularly useful for preparing compositions which have high resistivities, e.g. 1000 ohm.cm or more, and which can be prepared with a high degree of reproduceability.