Abstract: A Pt/Ba_0.6Sr_0.4TiO₃ (BST)/La_0.5Sr_0.5CoO₃ (LSCO) ferroelectric capacitor was fabricated on (001) LaAlO₃ single crystal substrate using off-axis magnetron sputtering technology. The structure, morphology, and various properties, including dielectric, leakage, and energy storage performance of the BST film, were investigated in detail. The results indicate that the BST thin film is grown epitaxially and has a smooth and dense surface with a root mean square roughness of 1.228 nm. The Pt/BST/LSCO capacitor exhibits excellent dielectric properties with tunability and maximum loss of 73.73% and 0.078 at a frequency of 100 kHz, respectively, as well as lower leakage current densities (on the order of 10^-6 A/cm²). In addition, the BST thin film demonstrates favorable energy storage performance and temperature stability. At a frequency of 10 kHz and an applied electric field of 2 000 kV/cm, the total energy storage density, effective energy storage density, and energy storage efficiency at room temperature are 27.01 J/cm³, 16.03 J/cm³, and 59.4%, respectively. With increasing temperature up to 105 ℃, the energy storage efficiency can reach as high as 72.2% with an applied electric field of 1 200 kV/cm, which can be attributed to the higher temperature promoting the thermal movement of ions, thereby effectively improving the energy storage efficiency.