A diffuse-interface field approach is developed to model the evolution of aggregate in sintering ceramics. The aggregate microstructure is characterized by a relative density field, and multiple long-range order (LRO) parameter fields representing the crystallographic orientation of grains. The evolution of the density field is governed by Cahn-Hilliard equation, while the LRO orientation fields by the Time-Dependent Ginzburg-Landau equation (TDGL). The nonlinear dynamic equations are solved efficiently by a semi-implicit Fourier-Spectral method, providing detailed information about particle contact, neck growth and pore spheroidization. The quantitative neck growth through multiple diffusion approaches is extracted from the simulation and compared with previous thermodynamic growth analysis. (C) 2003 Elsevier Science B.V. All rights reserved.