All sites’ systematic non-stoichiometric regulation of ordering-related structure and microstructure for enabling ultralow dielectric loss and temperature stability in Ba(Mg1/3Nb2/3)O3 perovskite ceramics

Abstract

This study employs non-stoichiometric design at distinct chemical sites within the perovskite structure to systematically investigate the influence of the oxygen octahedra state, B-site cation ordering, ordered domain, and grain size on the dielectric properties within the Ba(Mg_1/3Nb_2/3)O₃ system and identifies strategies for enhancing the properties in 1 : 2 ordered perovskite ceramics. Both A-site deficiency and B″-site excess are effective in substantially reducing the sintering temperature (reduced by 200–250 °C) of the Ba(Mg_1/3Nb_2/3)O₃ ceramics by reducing the required activation energy, which is beneficial for reducing energy consumption. Through its significant effect on the densification temperature, non-stoichiometry profoundly modifies the grain size and grain boundary density of the ceramics. It is found that non-stoichiometry effectively regulates the cation ordering degree and ordered domain in Ba(Mg_1/3Nb_2/3)O₃ ceramics by fundamentally altering the kinetics and pathway of its formation. It is demonstrated that within a single phase, densely ordered perovskite ceramics, grain size and cation ordering degree jointly modulate the quality factor. Notably, the contribution of the ordering degree to the Q × f exhibits a critical grain size effect, as confirmed through systematic investigation. Ultra-high values of the quality factor (Q × f = 111 500 GHz) were attained in Mg-deficient samples, attributed to a favorable balance between grain boundary loss and cation ordering degree; this value represents an increase by a factor of nearly two compared with that of the stoichiometric composition (Q × f = 54 800 GHz). Furthermore, non-stoichiometry significantly reduces τ_f through the modulation of oxygen octahedral tilting, thereby enhancing temperature stability. This study provides a viable strategy for modulating the microwave dielectric properties of ordered perovskite microwave dielectric ceramics.