The synthesis of nano-sized La
9.33Ge
6O
26 powders with apatite-type structure by sol–gel auto-combustion method has been investigated. The details of gel's auto-combustion were investigated by DTA-TG and the structure of as-synthesized powders from auto-combustion was charactered by XRD and TEM. The results show that single phase La
9.33Ge
6O
26 powders with average size of
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50 nm can be directly synthesized by sol–gel auto-combustion. The as-synthesized powders exhibited high sinter activity, it can be sintered to 94 % of its theoretical density at 1150 °C for 4 h, about 200 °C lower than the sintering temperature for the powder derived from traditional solid reactions. The La
9.33Ge
6O
26 electrolyte sintered at 1150 °C for 4 h has relatively high oxide ionic conductivities (
σ750 °C = 0.01 S/cm), moderate thermal expansion (TECs = 9.82 × 10
−6 K
−1, between room temperature and 1000 °C) and low electrical activation energy (
Ea = 1.02 eV).
