Relaxor dielectric properties of a (Ca 1.5Ti 0.5)(NbTi)O 7 ‘misplaced-displacive’ cubic pyrochlore synthesised via metallorganic decomposition

Abstract

A ‘misplaced-displacive’ Ca 1.5NbTi 1.5O 7 (CNT) Fd 3 ̄ m , cubic pyrochlore phase ( a = 10.2171 Å ) has been successfully synthesised via a metallorganic decomposition route, enabling a much lower final annealing temperature than the conventional solid state reaction route. This CNT pyrochlore has a very similar stoichiometry to the family of misplaced-displacive Bi-based cubic pyrochlores (BBCPs), except that both the cation and anion sites of the ideal A 2B 2O 7 pyrochlore structure type are fully occupied. Essentially identical dielectric properties of the BBCPs were found with a relatively high dielectric constant of 103 and a relatively low dielectric loss of 0.009 at 100 kHz at room temperature, as well as typical relaxor dielectric behaviour at lower temperatures. The lower temperature dielectric relaxation behaviour observed in BBCPs is thus not inextricably linked to the presence of bismuth on the ideal pyrochlore A site. This provides an important new insight into the dielectric relaxation behaviour of misplaced-displacive cubic pyrochlores.