Low thermal expansion materials from solid solutions NaGe2-xTix(PO4)3 (x = 0.25, 0.5, 0.8, 1) with NZP structure have been obtained by solid state reaction. Lattice thermal expansion coefficients have been determined from x-ray diffraction data at temperatures ranging from 26 to 800-degrees-C. Evolution of the thermal expansion with composition has been studied. The thermal expansion coefficient in the a direction decreases from 1.348 x 10(-5)degrees-C-1 to 0.8340 x 10(-5)degrees-C-1 and the thermal expansion coefficient in the c direction increases from 1.244 x 10(-5)degrees-C-1 to 1.743 x 10(-5)degrees-C-1 with increasing x, with a deflection in the composition with x = 0.5. Evolution of macroscopic thermal expansion with composition has been studied by dilatometry measurements. DSC measurements have been also carried out on these samples. Composition with x = 1, NaGeTi(PO4)3, shows a different thermal behavior from those of the other solid solutions with higher Ge content, which present an isotropic thermal expansion as germanium compound does.