Sol-Gel Derived Ba x Sr 1−x TiO 3 Films for Microwave Applications

ISSN： 0015-0193

Source： Ferroelectrics, Vol.329, Iss.1, 2005-01, pp. : 39-42

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Abstract

Measured capacitance as a function of voltage, at a frequency of 1 MHz is reported for sol-gel deposited Barium-Strontium Titanate (Ba x Sr 1−x TiO 3 ) thin films with x = 0.0 to 1.0. Tunability is defined as the percentage change of the dielectric constant from its zero-bias value in the presence of a dc biasing electric field. Tunability increases as we move from x = 0.0 to x = 0.8, there is a slight decrease in tunability with further increase in x. Fatigue reduces tunability so it will be desirable to have the films in the paraelectric phase. Tunability of various compositions are examined as a function of field, thickness and temperature. For all compositions tunability shows a peak near the phase transition temperature. The composition range 0.4 to 0.6 appears most suitable for tunable phase shifter as these compositions are in the paraelectric phase at room temperature, tunability is high and the effect of composition in this range is small.