Enhanced dielectric and tunable properties of barium strontium titanate thin films through introducing Nd(Zn_1/2Ti_1/2)O₃ and adjusting Ba/Sr

Ba_0.6Sr_0.4TiO₃ (BST) and 0.06Nd(Zn_1/2Ti_1/2)O₃–0.94Ba _x Sr_1−x TiO₃ (NZT–BST) thin films with x = 0.6, 0.7, 0.75, and 0.8 were fabricated on Pt/Ti/SiO₂/Si substrates by sol–gel method. The structures, surface morphology, dielectric, and ferroelectric properties, and thermal stability of BST and NZT–BST thin films were investigated as a function of NZT and Ba content. It was found that introducing NZT into BST decreased significantly dielectric loss, however, along with the tunability. On this basis, increasing Ba/Sr in NZT–BST thin films led to the simultaneous increase of dielectric constant and tunability of thin films. As a result, optimized dielectric and tunable properties were obtained for 0.06Nd(Zn_1/2Ti_1/2)O₃–0.94Ba_0.7Sr_0.3TiO₃ thin film with the highest FOM value of 43.22. It awakens us that, for reducing dielectric loss, introducing a certain amount of low permittivity oxides or non-ferroelectrics like NZT into weak ferroelectric perovskite tunable materials, not into paraelectric perovskite tunable materials, may obtain more excellent dielectric and tunable performances.