Evaluation of Co- and Pr-Doped Zinc Silicate Powders by Photoacoustic Spectroscopy

Abstract

Photoacoustic (PA) spectroscopy was applied to evaluate the roles of Co and Pr in Zn2SiO4:Co and Zn2SiO4:Pr powders in relation to non-radiative transitions. These samples were prepared by dry reaction within an evacuated silica glass tube, where the sintering temperature was 800, 900, or 1000 °C. The Co and Pr concentrations were adjusted to a stoichiometry of Zn1.82SiO4:M(Co or Pr)0.18. From the results of X-ray diffraction (XRD) analysis, all samples indicated a rhombohedral structure (R3) of Zn2SiO4; however, the formation of Zn2SiO4 was not enhanced below a sintering temperature of 900 °C. PA spectra in the visible range of all samples reflected the coloration of samples and the XRD results. The Co-ion and Pr-ion in Zn2SiO4:Co and Zn2SiO4:Pr were assumed to behave as non-radiative centers in the visible range. Furthermore, for Zn2SiO4:Co sintered at 1000 °C, PA spectroscopy could extract new information about the location of unknown non-radiative levels between 390 and 470 nm.

Electronic structures of two types of TiO2 electrodes: inverse opal and nanoparticulate cases

“…49 The PA signal is less sensitive to light scattering effects than conventional transmission signals. 21,25,26,[50][51][52] The PA sensitivity is higher for weak absorption than that of conventional transmission techniques due to the induced thermal energy. Hence, the technique is useful not only for optical absorption edge characterization but also for sub bandgap characterization.…”

Adsorption and Electronic Structure of CdSe Quantum Dots on Single Crystal ZnO: A Basic Study of Quantum Dot-Sensitization System

“…Optical absorption information is important in order to study the electronic structure of CdSe QDs on single crystal ZnO and to carry out studies on photosensitization in QDSCs. Optical absorption has been measured using photoacoustic (PA) spectroscopy. ,− The PA technique detects acoustic waves resulting from heat modulated through nonradiative de-excitation processes in materials. The PA signal is insensitive to light scattering, and the sensitivity of the signal is higher than that of the transmission technique.…”

Correlation between crystal growth and photosensitization of nanostructured TiO2 electrodes using supporting Ti substrates by self-assembled CdSe quantum dots

“…Changes of sample temperature by photothermal phenomenon (proportional to optical absorption) generate pressure changes in the enclosed gas that are converted to electrical signal by the microphone. The application of PA spectroscopy for the characterization of the electronic, optical, defect structures and thermal properties of semiconductors is important and has been demonstrated [9][10][11][12][13][14][15][23][24][25][26][27][28][29][30]. IPCE spectroscopy is a photoelectrochemical technique and it can evaluate the total quantum yield for (1) the electron injection from the CdSe QDs to the conduction band of TiO 2 , (2) the collection efficiency of the injected electrons at the back contact and (3) the hole transfer efficiency to the electrolyte.…”