Processing of electroceramics using mechanical activation

By using intensive milling of a mixture of two or more precursor powders, it is possible to induce a chemical reaction among them and to produce new compounds (reactive milling) or, it is also possible to dissolve one into the others (mechanical alloying) and end up with a solid solution. When such events are activated, the intensive milling is known as Mechanical Activation. In addition, intensive milling commonly produces particle size reduction and good homogeneity in the final product. All these characteristics in a powder might improve the performance of the final electronic device. Electroceramics such as BaTiO₃ are frequently applied with additions of several dopants. These dopants can be dissolved into the BaTiO₃ crystalline lattice by intensive milling without a solubilization treatment. When a mixture of powders in the system Bi2O₃-TiO₂ is milled, an amorphous phase is obtained. Then, applying a suitable thermal treatment, very small crystalline particles of a bismuth titanate could be produced. A very homogeneous mixture of fine particles might produce better ZnO based varistors. Very small grain size can, in principle, render high values of breakdown fields, and a well mixed powder formulation could produce high values of the nonlinearity coefficient. Some years ago, researchers were skeptical about the potential of these techniques to produce materials for electronic purposes, since the contamination from the milling media appeared to be a serious drawback. Nowadays it is clear that materials for electronic applications can be fabricated with improved properties when a suitable milling media is chosen.