Improved dielectric tunability of PZT/BST multilayer thin films on Ti substrates

PbZr0.2Ti0.8O3/Ba0.6Sr0.4TiO3 (PZT/BST) multilayer thin films on LaNiO3 buffered Ti substrates were fabricated by sol-gel method. Results show that there are tetragonal PZT phase and cubic BST phase in the phase structure of PZT/BST films. These films with small grain size also exhibit enhanced dielectric temperature stability and reduced leakage current density. Dielectric anomaly is found for such PZT/BST multilayers: the maximum of dielectric constant and tunability respectively reaches 501 and 41.1% (400 kV/cm) when the thickness content of BST films is 50%. The corresponding temperature coefficient of permittivity (TCP) is only 2.7 × 10−4/°C. Furthermore, dielectric constant and tunability of such PZT/BST thin films are calculated by phenomenological theory. The experimental data of dielectric constant and tunability are both in between the calculated results of without and complete electrostatic coupling, indicating that dielectric anomaly is caused by electrostatic coupling and part coupling takes place in the fabricated films.