Dielectric pyrochlores in bismuth magnesium tantalate ternary system
Tan Kar Ban. (2012) Dielectric pyrochlores in bismuth magnesium tantalate ternary system.
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Ceramic compositions produced in this invention include Bi3Â¬Mg2Ta3O14 , Bi2Mg2/3Ta4/3O7 and Bi3+(5/2)xMg2-xTa3-(3/2)xO14-x; phase pure subsolidus solution as represented by Bi3+(5/2)xMg2-xTa3-(3/2)xO14-x, wherein 0.12 â‰¤ x â‰¤ 0.22 able to be produced. This invention also discloses a method of preparation of the BMT pyrochlore, in which Bi2O3, MgO and Ta2O5 in stoichiometric amounts are mixed homogeneously with acetone, pre-treated at 300 Â°C to 600 Â°C for at least one hour to ensure that the Bi2O3 reacts to form less-volatile compounds, the pretreated powders are subsequently heated at 800 ÂºC overnight, and further synthesised at 1025 ÂºC for 48 hours, preferably with intermediate regrinding. The compositions of invention have outstanding bulk dielectric properties, e.g., Îµâ€™ values of between 74 â€“ 85 at frequency 1 MHz at ~25oC, TCÎµâ€™ of -158 to -328 ppm/Â°C at 1 MHz in the range of ~25Â°C - 300Â°C and tan Î´ in the order of 10-3 at 1 MHz, ~25oC .
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