GRAIN-ORIENTATION AND ELECTRICAL-PROPERTIES OF SR2NB2O7 CERAMICS

Sr2Nb2O7 ceramics sintered at 1753 K and the hot-pressed compacts annealed at 1073 K possess low density because of the formation of voids by large expansion. The expansion is attributed to cleavage and due to the preferential grain growth along the [0 1 0] direction. An increase in dielectric constant at temperatures over 973 K and a parabolic decrease of resistivity with increasing temperature are observed. The constant variation corresponds well to the decrease in thermal strain and the grain orientation factor along the [0 k 0] direction.