  Compared to AgNbO3 based ceramics, the experimental investigations on the
single crystalline AgNbO3, especially the ground state and ferroic domain
structures, are not on the same level. Here in this work, based on successfully
synthesized AgNbO3 single crystal using flux method, we observed the
coexistence of ferroelastic and ferrielectric domain structures by a
combination study of polarized light microscopy and piezoresponse force
microscope, this finding may provide a new aspect for studying AgNbO3. The
result also suggests a weak electromechanical response from the ferrielectric
phase of AgNbO3 which is also supported by the transmission electron microscope
characterization. Our results reveal that the AgNbO3 single crystal is in a
polar ferrielectric phase at room temperature, clarifying its ground state
which is controversial from the AgNbO3 ceramic materials.
