Self-assembled porous ZnGa2O4 particles were synthesized through a facile hydrothermal route in this work. The phase evolution and microstructure of specimens were identified by XRD and SEM. Various morphologies (i.e. porous, nanorods or spherical particles) and size (nano or micro-sized) could be rationally designed through altering the reaction conditions. Hydrothermal ZnGa2O4 particles exhibited an outstanding microwave dielectric performance, i.e. a dielectric constant of 9.93, a Q x f value of 73 000 GHz, and a tau(f) value of -68.7 ppm/degrees C. What is more, the ZnGa2O4 ceramics displayed a stable quality factor in the high temperature region (1400-1500 degrees C) due to the unique frame-structured ZnGa2O4 particles. Therefore, they can be regarded as potential candidate materials for millimeter-wave device. (C) 2015 Elsevier B.V. All rights reserved.