Preparation of Ba0.09Sr0.91TiO3/YBa2Cu3O7 − x bilayers and investigation of their dielectric properties

• The BST/YBCO and BST/LNO bilayers were prepared via sol–gel method.
• The dielectric properties of BST/YBCO and BST/LNO structures were compared.
• The low temperature dielectric properties of BST/YBCO and BST/LNO were studied.

YBa2Cu3O7 − x (YBCO) films of 110 nm thickness were prepared on LaAlO3 (LAO) substrates via the sol–gel method. Subsequently, about 400 nm thick Ba0.09Sr0.91TiO3 (BST) films were epitaxially grown on the YBCO and LNO films surface; the BST films exhibited a strong c-axis orientation. The dielectric adjustability and relative dielectric constant was investigated in the range of 300-83 K. Results indicate that the tunability of the Ba0.09Sr0.91TiO3/YBa2Cu3O7 − x (BST/YBCO) displayed an increase relative to c-axis-oriented BST on LaNiO3 (LNO). The tunability was further enhanced as the operating temperature decreased, yet the loss tangent (tanδ) decreased. The tunability and the tanδ at 100 kHz and 83 K were 58% and 0.029, respectively.