Luminescence of the B2Σ+-X2Σ+ band system of AlO during plasma electrolytic oxidation of aluminum

► Plasma electrolytic oxidation (PEO) of aluminum in citric acid. ► Luminescence of the B2Σ+-X2Σ+ band system of AlO during PEO. ► The measured intensity distributions are employed to estimate the mean plasma temperature. ► The composition of plasma containing aluminum and oxygen is calculated.