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The Ho3+/Yb3+ doped Y2O3 phosphor samples were synthesized through a combustion method and then were annealed at 800 °C, 1000 °C, and 1200 °C.

Photoacoustic spectrometer (PAS) is a significant technique to measure the thermal diffusivity of any material. When modulated light interact with solid sample which is covered by aluminium or other metal plate, first the light is absorbed by the sample and then thermal energy emitted due to non-radiative decay. Thereafter, acoustic wave produced due to different temperature which maintain by an optical chopper. The medium inside the cavity expands or retract according to the chopper frequency. So, the generated pressure fluctuation inside it measures by using a sensitive condenser microphone which fitted inside the cavity by a narrow path. Here the authors successfully synthesized molybdenum disulfide (MoS2) and its nanocomposite with graphene oxide (MoS2-GO) by simple hydrothermal method. The XRD and FESEM data confirm the phase and morphological structures of the synthesized material. The thermal diffusivity of MoS2 and MoS2-GO nanocomposite are obtained 10.94 mm2/s and 14.72 mm2/s respectively.

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Photoacoustic spectroscopy (PAS) is an important technique for the characterization of materials by measuring the heat produced due to the non-radiative transitions. Here, the authors have fabricated a photoacoustic cell and made parametric studies to get maximum signal sensitivity. For the optimum signal, the cavity volume of the sample chamber is found to be 1.763 × 10–6 m3. After optimization of the cell, the thermal diffusivity of hummers method synthesized graphene oxide (GO) powder was measured using laser excitation at 980 nm and it is found to ∼(1.84 ± 0.10) × 10–4 m2/s. Also, the thermal diffusivity of the same sample was measured using 560 and 680 nm excitation wavelengths. No measurable change in thermal diffusivity with excitation wavelength is seen and it confirms that thermal diffusivity is independent of the excitation wavelength. Lastly, photoacoustic spectrum of the GO sample was measured in the 400–1200 nm range and compared with the spectrum of lamp black.