Thermal study of an aluminium nitride ceramic heater for spray CVD on glass substrates by quantitative thermography

A thermographic approach is used to determine the temperature of an aluminium nitride hot plate as a glass substrate heater for depositing thin films by spray Chemical Vapour Deposition. In this context, the temperature of the hot plate is conditioned by the evaluation of both effective emissivity and environment temperature with a calibration curve of the commercial camera. We first examined the consistency of the thermosignal/temperature correspondence by employing the software calibration. The environment temperature is evaluated by means of a ruffled aluminium foil according to ASTM. The effective emissivity is measured in situ by using a commercial IR camera in the temperature range 40-540 degrees C with a better than 3% accuracy. Absolute value of effective emissivity is in agreement with spectrometric values up to 120 degrees C. Above this temperature, a strong dependence with temperature is highlighted. The radiometric temperature values are, thereby, corrected with an exactitude of temperature better than 2.5% in Celsius degree for the highest temperatures considered.