During solid-state sintering a powder compact is gradually transformed into a solid body by means of diffusional processes. Usually the processes are accompanied by a loss in porosity and densification. This densification process is driven by the reduction of the total surface energy of the sintered body. A phase-field method, based on a Gibbs energy functional and the Cahn-Hilliard equation, is formulated to study the microstructural evolution of particles during solid-state sintering. At present a simple model for a one-component system is considered and the simulations are performed in 2D. Already this model reveals the complex morphological development during sintering. However, our long-term goal is to apply thermodynamic functions assessed by the CALPHAD technique which will allow simulation of complex multi-component and multiphase materials, e.g. cemented carbides.