Investigation of Ag(Ta,Nb)O3 as tunable microwave dielectric

Ag(Ta,Nb)O-3 (ATN) has been investigated as a candidate material for an application in tunable high frequency devices. AgTa0.1Nb0.9O3 as a bulk ceramic shows moderate permittivity of epsilon = 310 and visible tunability tau = (epsilon(0) - epsilon(E-max))/epsilon(0) of 16% for an applied field of 10 kV/cm at room temperature. AgTaxNb1-xO3 powders with 0less than or equal toxless than or equal to0.4 have been prepared by mixed oxide technique. Permittivity, losses and tunability of ATN bulk ceramic and screen printed thick films have been characterized at frequencies < 1 MHz in the temperature range from - 150 degreesC to + 120 degreesC. Increasing the tantalum content leads to an increase of the tunability and a shift of the point of maximum tunability to lower temperatures. ATN thick films have also been characterized up to 12 GHz in the temperature range from -30 degreesC to + 100 degreesC by using coplanar waveguide resonators. A decrease of tunability to tau < 1% with increasing frequency has been observed. The beginning of dielectric relaxation is observed at frequency of about 8 GHz. (C) 2003 Elsevier Ltd. All rights reserved.