Thermal characterisation of red clay from the Northern Region of Rio de Janeiro State, Brazil using an open photoacoustic cell, in relation to structural changes on firing

Abstract Values of some thermal properties and the crystalline phases of red ceramic samples from the Northern region of Rio de Janeiro state in Brazil are reported as a function of firing temperature (900, 950, 980, 1020, 1060 and 1100 °C). The open photoacoustic cell (OPC) technique and a continuous light illumination photothermal method were employed in order to obtain the thermophysical characteristics: thermal diffusivity (α) and specific heat capacity (ρc), respectively. Indirectly, using simple mathematical relations, the thermal conductivity (k) and the thermal effusivity (e) were obtained. Crystalline phases were identified by X-ray diffraction (XRD). The intrinsic relationship between the structure and the thermal diffusivity was analysed.