Ceria based electrolytes were fabricated by a plasma spraying method. The porosity which was crated during the plasma spraying process was infiltrated with Ce0.8Gd0.2O2 sol by ultrasonic treatment and heat treatment at 90$0^{circ}C$ in order to improve physical and electrical properties. The porosity decreased from 9.8% to 6.5% and gas permeability at 80$0^{circ}C$ decreased from 16.7$ imes$10-3 to 5.7$ imes$10-3 cm3(STP)/cm2.s.cmHg as the number of treatment increased 10 cycles. The ionic conductivity was also increased about 30% after 10 times of sealing.