Improvement in conductance modulation linearity of artificial synapses based on NaNbO3 memristor

•Switching behavior of NaNbO3 is explained by growth/dissolution of the filament.•Nonlinear conduction modulation is related to the nonlinear growth of the filament.•Filament growth is controlled by redox process with increase of O2 vacancy number.•Conductance modulation linearity is improved by increase of O2 vacancy number.•NaNbO3 memristor shows synaptic plasticity with good linear conduction modulation.