High performance films of binary system SrTiO₃-PbZr_0.52Ti_0.48O₃ on sapphire

Abstract

Continuous series of solid solutions x.SrTiO₃-(l-x).PbZr_0.52Ti_0.48O₃ (SPZT) have been grown by pulsed laser deposition technique onto La_0.7Sr_0.3CoO₃/Al₂O₃(0112) single crystal. Films properties have been characterized in Au/SPZT/La_0–7Sr_0.3CoO₃(LSCO)/Al₂O₃ vertical capacitive cell. X-ray diffraction shows SPZT/LSCO bilayer grows in strict epitaxial relationship with sapphire substrate:

Display Equation

LSCO layer was found to be tensile strained, while SPZT film experiences tetragonal distortions c/a −1 ≈ 0.86% which are much lower than 2.73% in pure PZT ceramics. Curie temperature in SPZT film has been tailored continuously in the explored temperature range 77 K to 400 K by controlling SrTiO₃:PZT ratio. Processing parameters have been optimized to get the highest tenability factor . SrTiO₃:PZT=83:17 film exhibits superior properties: at 1 kHz maximum dielectric permittivity and minimum loss tanδ were found to be 870 and 0.005, respectively; while K-factor exceeds value of 60 in the temperature range 280 to 350 °C reachingthe maximum value of 64 at 325 °C. SPZT films can withstand prolonged pre-breakdown electric field and has resistivity as high as 3.5 10¹² Ω cm at 186 kV/cm.

Key Words:

• epitaxial films
• tailoring ferroelectricity by alloying
• low loss
• voltage tunability.