Abstract: There is provided a sealing glass composite which has a desired coefficient of thermal expansion. The composite is made up of a glass matrix having a first coefficient of thermal expansion and a substantially spherical particulate additive with a second coefficient of thermal expansion dispersed within the matrix. Use of a substantially spherical particulate additive having a reduced surface area as compared to other shaped particulate additive minimizes the reaction between the additive and the glass matrix. The spherical particles also provide better flow at high loading factors and improved fracture toughness.