Pyrochlore formation and its dielectric properties within Bi 2 O 3 –TiO 2 –WO 3 ternary system

Abstract

Using X-ray diffraction and SEM methods, as well as measurements of the microwave dielectric properties, a section of the ternary Bi₂O₃–TiO₂–WO₃ system has been investigated at 1100°C. Within this system the formation of pyrochlore has been detected, and it was revealed that WO₃ incorporates into the B sites of the pyrochlore crystal lattice. Charge compensation due to W⁶⁺ incorporation occurs primarily via the formation of A site vacancies. With this addition the pyrochlore's unit cell decreases, and reaches its lowest value for ∼13 mol.-% of added WO₃. The permittivity of the pyrochlore phase is relatively high and decreases with increasing W content, whereas Q × f increases with increasing W content.