Photoacoustic spectra of BaBi1xPbxO3 (x = 0.0, 0.65, and 1.0)

Photoacoustic (PA) spectroscopy is applied to study the heat generation by nonradiative processes of BaBiO3 (semiconductor). BaBi0.35Pb0.65O3 (metal semiconductor transition region), and BaPbO3 (metal) powdered samples over the wavelength range from 330 to 1200 nm with a modulation frequency of 33 Hz. PA spectroscopy can provide optical absorption spectra, qualitatively, for opaque samples such as powders. In the PA signal intensity spectra, the maximum peaks are observed at 2.5. 1.8. and 1.5 eV for BaBiO3, BaBi0.65Pb0.65O3. and BaPbO3, respectively. Also, the changes of PA signal phases are observed at 1.8 and 1.5 eV for BaBi0.35Pb0.65O3 and BaPbO3, respectively. As the PA signal intensities and phases are affected by the plasma edge, those peaks are related to the band gap of BaBiO3 (2.5 eV) and plasma frequencies of BaBi0.35Pb0.65O3, and BaPbO3 (1.8 and 1.5 eV, respectively).