In recent years, due to the need for saving energy and reducing greenhouse gases, high-efficiency power generation plants have been developed. In power generating gas turbine plants, improvements in efficiency have been achieved by increasing turbine inlet gas temperature. Hot section components, such as combustors, rotating blades and vanes, are exposed to high temperature environments for prolonged periods of time. Accordingly, the materials for these components need resistance to oxidation and sulfurization at high temperatures. Therefore, thermal barrier coatings (TBCs) are an importnat component of advanced gas turbines that require high reliability and endurance. However, thermally grown oxide (TGO) forms at the interface between the ceramic top coating and metallic bond coating of TBCs during service. Delamination or spallation at the interface can be occurred by the TGO formation and growth. Therefore, formation and growth behavior of TGO were considered. Modifications of the bond coating materials are one means to inhibit the TGO formation and to improve the bonding strength of TBCs. In this study, morphologies of TGO were controlled by Ce and Si addition to conventional CoNiCrAlY bond coating material. As a result, when the TBCs with Ce added bond coating materials were aged at 1100^oC for 100 hours, morphologies of TGO were changed drastically. It was hoped that the morphologies can improve bonding strength of TBCs. Therefore, we performed experiments in order to measure the bonding strength of the conventional TBC and the TBC with modified bond-coat by four-point bending tests. Results show the modified TBC had higher bonding strength than the conventional one. We succeeded in producing a TBC with a bond strength that is three times higher than conventional TBC.