  Memristors have been intensively studied in recent years as promising
building blocks for next-generation non-volatile memory, artificial neural
networks and brain-inspired computing systems. Even though the environment
adaptability of memristor has been required in many application fields, it has
been rarely reported due to the underlying mechanism could become invalid
especially at an elevated temperature. Here, we focus on achieving synaptic
learning and memory functions in BiFeO3 memristor in a wide range of
temperature. We have proved the ferroelectricity of BFO films at a record-high
temperature of 500 {\deg}C by piezoresponse force microscopy (PFM) measurement.
Due to the robust ferroelectricity of BFO thin film, an analog-like resistance
switching behavior has been clearly found in a wide range of temperature, which
is attributed to the reversal of ferroelectric polarization. Various synaptic
functions including long-term potentiation (LTP), depression (LTD), consecutive
potentiation/depression (P/D) and spike-timing dependent plasticity (STDP) have
been realized from -170 to 300 {\deg}C, illustrating their potential for
electronic applications even under extreme environmental temperature.
