The effect of texture with (100) and (110) preferred orientations on dielectric properties of Ba0.6Sr0.4TiO3 (BST) thin films grown on SrO (9nm) and CeO2 (70nm) buffered Si substrates, respectively, was investigated. The coplanar waveguide (CPW) phase shifter using (100) oriented BST films on SrO buffered Si exhibited a much-enhanced figure of merit of 24.7°∕dB, as compared to that (10.2°∕dB) of a CPW phase shifter using (110) oriented BST films on CeO2 buffered Si at 12GHz. This work demonstrates that the microwave properties of the Si-integrated BST thin films are highly correlated with crystal orientation.
We report on the facile synthesis of highly conductive RuO 2 /Mn 3 O 4 composite nanofiber mats by electrospinning of mixed ruthenium and manganese precurosr solution and their potential suitability as an active electrode in electrochemical capacitors. Electrospun RuO 2 /Mn 3 O 4 fiber mats calcined at 300 C exhibit multiple fiber networks composed of nanoparticles in a size range of 5-10 nm (average % 7.5 nm). Partially crystalline Mn 3 O 4 phases are well mixed with the amorphous RuO x (a-RuO 2 ) phases while pure Mn 3 O 4 fibers exhibit only crystalline phase. Electrochemical capacitors utilizing a-RuO 2 /Mn 3 O 4 fiber mats show a high specific capacitance of 293 Fg À1 at 10 mVs À1 , high rate capability with a capacity loss of only 45% from 10 to 2000 mVs À1 , and superior cycle performance of over 30,000 cycles as compared to those characteristics of Mn 3 O 4 fiber mats (216 Fg À1 at 10 mVs À1 , capacity loss of 94% at 2000 mVs À1 , poor cycle performance of 2000 cycles). These results are correlated with the improved mixed ionic/ electronic conductivity of the a-RuO 2 /Mn 3 O 4 fiber mats as well as to its morphological evolution, i.e., highly porous flower-likefiber networks, during cycling tests.
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