Knowing the thermal expansion of a material and the correlation analysis of the photoacoustic signals, it is possible to obtain the phase transition temperature and a qualitative curve of the specific heat at constant pressure (Cp) for ceramic materials. This analysis was applied to a BaTiO3 ferroelectric ceramic and a good agreement with previously published Cp versus temperature curves was obtained. Additionally, the phase transition temperature and the Cp curve of a samarium-doped lead titanate ceramic (Pb0.88Sm0.08TiO3) are presented. The phase transition temperature of the Pb0.88Sm0.08TiO3 obtained with this technique was corroborated with classical differential thermal analysis and dielectric permittivity measurements.
An experimental investigation of the thermal behaviour of the
dissolution process of the Suzuki phase (SP) by continuous heating
(1 °C min−1)
of KBr:Eu2+
crystals is reported in this work. The thermal profiles were determined by the correlation functions
between subsequent photoacoustic (PA) signals registered during the dissolution process.
The behaviour of the thermal profile is directly related to the absorption coefficient of the
Eu2+
ion in precipitated states that are present in the crystal. The PA signal is detected as a consequence
of the non-radiative processes that take place after the excitation of the low-energy band of the
Eu2+
ion by means of a focused laser pulse at 355 nm. The results obtained by
this method are compared with those simultaneously obtained by the
photoluminescence (PL) technique. The samples were heated from room temperature to
205 °C.
The PA signal and PL spectrum were obtained every
6 °C.
The temperature range of the SP dissolution process was from 77 to
115 °C.
These results are in agreement with those obtained by the PL technique and with the data
reported in the literature.
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