'Parameters Controlling X7R Behaviour in BT Based Dielectrics'

摘要

X7R is one of the most important types of class II dielectrics used in bulk and Multilayer capacitors. In X7R type the dielectric response as a function of temperature is flattened and controlled to within +-15% between -55μ & +125℃. In Barium Titanate based dielectrics, a fine-grained core-shell microstructure formed due to the inhomogeneous distribution of additives is known to influence X7R behavior. This paper analyzes systematically the parameters that control the X7R behavior. It is found that the concentration of donor, donor to acceptor ratio, sintering temperature, sintering schedule and atmosphere of sintering in combination with core-shell microstructure controls the X7R behavior. All these parameters are interconnected and there is definite interrelationship between these parameters. Variation of one parameter in rum affects other parameters. The results are discussed based on BaTiO_3-CaZrO_3-Nb_2O_5-Co_3O_4. Proper control of this combination of parameters is essential for the development of X7R composition. Thorough knowledge about the interrelationship between these parameters can give the capacitor component industry, a wider processing window and hence improved yield.