To improve the unit cell performance and stability, molten carbonate fuel cell (MCFC) matrices were fabricated using synthetic alpha-LiAlO2 powder and they showed mechanical and microstructural stability under thermal cycle tests. The pure alpha-LiAlO2 matrix demonstrated stability with high open-circuit voltage (OCV) and maximum power density during many thermal cycle tests (more than 15 repetitions). Furthermore, to minimize the change in stack height during stack start-up and to improve mechanical and microstructural stabilities of the matrix, the electrolyte-combined alpha-LiAlO2 matrix was optimized by controlling the mixing ratio of synthetic alpha-LiAlO2 and Li/K carbonate powders. The suitable electrolyte content was fixed at approximately 50 vol.% for the homogeneously filled pores of the pure alpha-LiAlO2 matrix. These matrices showed good microstructural stability during five thermal cycle tests in an air atmosphere at 923 K and with improved unit cell performance (0.127 W cm(-2)) under MCFC operating conditions. In unit cell and thermal cycling tests, the optimized matrices were stable through more than 20 repetitions. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.