Glass composition, preparation method of glass composition, and cooking appliance

A cooking device comprising:

• a cavity portion having a heating space defined therein;
• a door to provide access to the heating space;
• and
• at least one heat source to supply heat inside the heating space,
• wherein at least one of the cavity portion and the door comprises a metal base, and a functional layer disposed on the metal base,
• wherein the functional layer comprises a glass frit comprising P2O5, SiO2, B2O3, Al2O3, ZrO2 group I-based oxide, a fluorinated compound including at least one of NaF, CaF2 and AlF3, and an adhesion-enhancing component including at least one of Co3O4, NiO, Fe2O3 and MnO2,
• wherein P2O5 is contained in an amount that is greater than 25 wt % and less than or equal to 40 wt % based on a total weight of the glass frit,
• SiO2 is contained in an amount that is greater than or equal to 10 wt % and less than or equal to 25 wt % based on the total weight of the glass frit,
• B2O3 is contained in an amount of 3 wt % to 20 wt % based on the total weight of the glass frit,
• Al2O3 is contained in an amount of 7 to 24 wt % based on the total weight of the glass frit,
• ZrO2 is contained in an amount of 1 wt % to 7 wt % based on the total weight of the glass frit, and
• the group I-based oxide is contained in an amount of 7 wt % to 28 wt % based on the total weight of the glass frit,
• wherein the fluorinated compounds is contained in an amount of 0.1 wt % to 5 wt % based on the total weight of the glass frit,
• wherein the adhesion-enhancing component is contained in an amount of 1 wt % to 5 wt % based on the total weight of the glass frit,
• wherein the glass frit comprises more P2O5 than SiO2.