Simultaneous measurements of heat flux and thermal expansion on hyperfine multistage transitions of'single crystalline BaTiO3

The heat flux and the thermal expansion of BaTiO3 were simultaneously measured with a temperature resolution of milli-Kelvin to observe the multistage transitions. Heat flux was detected by the thermomodule and thermal expansion was detected by observing the change of capacitance due to the change of the sample length. At least six thermal anomalies were observed between 402 and 405 K in BaTiO3 simultaneously in heat flux and thermal expansion in the cooling process. The correspondence of the anomalies observed in the two physical properties was excellent. The thermal expansion curves along <0 0 1 > direction obtained at the cooling rates less than 20 muK s(-1) consisted of several steps with different number and magnitude depending on the cooling rate. The hysteresis behaviors for the phase transition of BaTiO3 are discussed in terms of domains. (C) 2003 Elsevier Science B.V. All rights reserved.