Nguyen Ngoc Minh, Bui Van Dan, Luong Xuan Dien, Phan Si Nguyen and Ngo Duc Quan 2021. EFFECT OF K-EXCESS ON ENERGY STORAGE DENSITY AND EFFICIENCY OF Bi0.5K0.5+xTiO3 FILMS. UTEHY Journal of Applied Science and Technology. 28, (Apr. 2021), 91-96.