NOVELTY - Vitroceramic glass composition comprises: a glass composition (A) having silica, aluminum oxide, calcium oxide, and optionally one/more oxides having zinc oxide, manganese dioxide, boric acid, chromium oxide and titanium dioxide; a glass composition (B) having silica, aluminum oxide, calcium oxide, strontium oxide, and optionally one/ more zinc oxide, manganese dioxide, boric acid, and chromium oxide; and a glass composition (C) having silica, aluminum oxide, lanthanum oxide and optionally one/more oxide having zinc oxide, manganese dioxide, boric acid, calcium oxide, and chromium oxide.    USE - The composition is useful for assembling of at least two parts; and for the preparation of the joint, assembling for high temperature electrolyzer or high-temperature fuel cell.    ADVANTAGE - The preparation of the composition is reliable, easy, simple and reproducible without including the use of the complex thermal cycles and stable, even with high temperature. The composition has high coefficient of expansion, and high chemically and mechanically resistant.    DETAILED DESCRIPTION - Vitroceramic glass composition comprises (in %): a glass composition (A) comprising 36-43 (preferably 36-42) mol.% of silica, 9-13 (9-12) mol.% of aluminum oxide, 38-50 of calcium oxide, and optionally one or more oxides comprising 4-5 mol.% of zinc oxide, 2-9 mol.% of manganese dioxide, 2-6 mol.% of boric oxides, 0.1-1 (preferably 0.4-1) mol.% of chromium oxide, and 0.1-4 (preferably 2-4) mol.% of titanium dioxide; a glass composition (B) comprising 43-48 mol.% of silica, 4-5 mol.% of aluminum oxide, 8-10 mol.% of calcium oxide, 34-39% of strontium oxide, and optionally one or more oxides comprising 4-5 mol.% of zinc oxide, 2-9 mol.% of manganese dioxide, 2-5 mol.% of boric oxide, and 0.1-1 mol.% of chromium oxide; and a glass composition (C) comprising 61-65 mol.% of silica, 14-15 mol.% of aluminum oxide, 18-20 mol.% of lanthanum oxide and possibly one or more oxide comprising 4-5 mol.% of zinc oxide, 4-5% of manganese dioxide, 2-3 mol.% of boric acid, 4-5 mol.% of calcium oxide, and 0.1-1 mol.% of chromium oxide. INDEPENDENT CLAIMS are included for:    (1) a process for assembling at least two parts, comprising (a) contacting the parts with a glass composition; (b) heating the assembled parts and the glass composition by maintaining temperature range, optionally separated or interrupted by one or more gradient of temperature at a heating rate of 0.5-3 degrees C/minute, to obtain a temperature T1 sufficient for softening the glass composition to form a joint between the parts, maintaining the parts at a temperature T2 less than or equal to T1 for a time sufficient for the glass composition solidifies and comprising more than 50 wt.% of crystalline phase, preferably 100 wt.% of crystalline phase, and cooling the parts and the joint to obtain room temperature or the operating temperature;    (2) a joint obtained by the process;    (3) a assembling obtained by the process; and    (4) a high temperature electrolyzer or high-temperature fuel cell comprising the joint or the assembly.