Pressure-Induced Ionic-Electronic Transition in BiVO_4

Electrical transport properties of bismuth vanadate (BiVO_4) are studied under high pressures with electrochemical impedance spectroscopy. A pressure-induced ionic-electronic transition is found in BiVO_4. Below 3.0 GPa, BiVO_4 has ionic conduction behavior. The ionic resistance decreases under high pressures due to the increasing migration rate of O^2- ions. Above 3.0 GPa the channels for ion migration are closed. Transport mechanism changes from the ionic to the electronic behavior. First-principles calculations show that bandgap width narrows under high pressures, causing the continuous decrease of electrical resistance of BiVO_4.