The sol-gel method was used to fabricate Pd-SiO2 membranes in which Pd particles 2-30 nm in size were dispersed in a SiO2 layer, and the thickness of the Pd-SiO2 layer was approximately 300 nm. The H-2 permeation properties and the thermal and hydrothermal stabilities of the Pd-SiO2 membranes were evaluated. In the present study, the Pd-SiO2 layer was fabricated by (1) a 1-step method, whereby calcination occurred only at 550 degrees C under a H-2 atmosphere for 1 h, and/or (2) via a 2-step method, whereby a first calcination was administered at 400 degrees C under a H-2 atmosphere for 1 h prior to a second calcination at 550 degrees C under a H-2 atmosphere for 1 h. The Pd-SiO2 membranes were quite stable under a N-2 atmosphere at 500 degrees C, irrespective of the membrane fabrication method (1-step, 2-step calcination). However, under a H-2 atmosphere, the N-2 permeance of a membrane fabricated using the 1-step method increased approximately 10 times after exposure to H-2 for the initial 3 h, and increased with time due to the formation of grain boundaries caused by the aggregation of Pd particles. A Pd-SiO2 membrane fabricated using the 2-step method was relatively stable under a H-2 and steam atmosphere (500 degrees C, steam: 70 kPa), and showed H-2 permeance of 5.0 x 10(-7) mol m(-2) s(-1) Pa-1 with H-2/N-2 and H-2/He permeance ratios of 260 and 2.2, respectively. The experimentally obtained H-2/He permeance ratio for Pd-SiO2 membranes (Si/Pd = 3/1, 317, 218, 119) showed reasonable agreement with a theoretical calculation based on a mixed-matrix structure (continuous phase: SiO2, dispersed phase: Pd). (C) 2013 Elsevier B.V. All rights reserved.