Nepheline solid solutions having high thermal expansion coefficients ranging from 1.2 to 1.8 x 10(-5)degrees C-1 were prepared from the systems NaAlSiO4-LiAlSiO4 and NaAlSiO4-KAlSiO4. The thermal expansion coefficient decreased by substituting Li+ for Na+, and increased by substituting K+ for Na+. By forming a series of the nepheline solid solutions in a single ceramic body, a functionally gradient material with respect to thermal expansion was prepared. The thermal expansion coefficient should gradually vary with position according to the composition x in Na(1-x)M(x)AlSiO(4) (M = Li and K).