A stoichiometric and 2mol% Ba deficient samples in the formulation 0.5BaTiO(3)-0.5BiMg(1/2)Ti(1/2)O(3) (BT-BMT) were processed via a mixed oxide solid-state route. The deficient sample exhibited a high relative permittivity (2100 +/- 15%) over the temperature range 90-450 degrees C and a low dielectric loss (tan < 0.01), maintained up to high temperature (430 degrees C). The samples exhibited intrinsic conduction mechanism and showed an n-type character. By introducing 2mol% Ba vacancies, a dramatic influence on the dielectric loss was observed which was mainly associated with the trapping of electrons by barium-oxygen vacancy pair associated with the intentionally produced cation vacancies. Thus, control of composition by creating deficiency allows fine tuning of the dielectric properties of BT-BMT ceramics for applications in high-temperature multilayered ceramic capacitors.