Isothermal section of the Na0.3CoO2H2O phase diagram at 22 °C from 11 to 100% relative humidity

An isothermal section of the Na0.3CoO2H2O system phase diagram at 22 °C from 11 to 100% relative humidity is presented. The superconducting Na0.3CoO2⋅1.2H2O phase is stable at a relative humidity (RH) higher than 30%; Na0.3CoO2⋅0.6H2O is the stable phase at RH below 30%. The unit cell parameters and temperature of superconducting transition of Na0.3CoO2⋅1.2H2O do not depend on relative humidity. The Na0.3CoO2⋅1.2H2O and Na0.3CoO2⋅0.6H2O hydrates are line phases and have a constant water content over the water vapor pressure range of their stability.