Improved Dielectric Properties of Heterostructured Ba_0.5Sr_0.5TiO_3 Thin Fiml Composites for Microwave Dielectric Devices

摘要

In the present work we have deposited MgO and Ba_0.5Sr_0.5TiO_3 (BST50) thin layers in different sequences to make MgO:BST50 hetero-structured thin films.These films wree characterized by X-ray diffraction and found to be highly (100) textured.The figure of merit [(C_0-C_v)/(C_(0·tandelta)} of the hetero-structured films was found to be higher as compared to pure BST50 films measured at 1 MHz frequency with electric field of 25.3 kV/cm.These films were used to make eight element coupled micro-strip phase shifter and characterized in a frequency range of 13-15 GHz.The hihg frequency figure of merit (kappa factor,defined as the ratio of degree of phase shift per dB loss) measured at around 14 GHz with electric field of 333 kV/cm has been markedly improved (around 64.28 deg/dB for hetero-structured film as compared to 24.65 deg/dB for pure film).Improvement in dielectric properties in a wide frequency range in the MgO:BST are believed to be due to the higher densification of the hetero-structured films.