Two-frequency operation in ceramic neodymium-doped yttrium aluminium garnet is demonstrated for 1.064 μm operation with a self-heterodyne beat-frequency tuning range in excess of 1.5 GHz. A 6 dB improvement of the peak-beat strength is seen in the ceramic material over that of similar crystalline Nd:YAG lasers. Experimentally, the ceramic host material is shown to have substantially higher polarization mode coupling constant, C = 0.72 ± 0.05, compared to crystalline Nd:YAG, C = 0.16 ± 0.05. The peak-beat strength is related to mode coupling. In general the Nd:ceramic YAG dual-frequency laser offers superior performance as a photonic-based radio-frequency source over Nd:YAG.