The effect of impurity phases on the structure and properties of microwave dielectrics based on complex perovskites Ba(Co1/32+Nb2/3)O3

Two major secondary phases have been revealed in the ceramics based on the complex perovskites Ba(Co1/3Nb2/3)O-3: a Ba-rich compound Ba8CoNb6O24 with the layered perovskite structure, and a Nb-rich compound with the structure of tetragonal tungsten bronze and the composition close to Ba6CoNb9O30. The presence of a small amount of the Ba-rich phase is accompanied with the rise in the quality factor (Q) of the material whereas the high amount is deleterious to Q. In contrast, the presence of even a small amount of Nb-rich phase always results in a sharp fall in the Q-factor. The ways of tuning temperature coefficient tau(f) in Ba(Co1/3Nb2/3)O-3 ceramics have been discussed.