PIN-PMN-PT single crystals near the morphotropic phase boundary with low level of In3+ doping were grown through slow cooling their high temperature solution. Temperature-dependent dielectric constants and pyroelectric coefficients indicated two phase transitions, i.e. orthorhombic (O)-tetragonal (T)-cubic (C), took place in 19PIN-45PMN-36PT single crystals upon heating from 35 degrees C to 250 degrees C. The dielectric constant of O phase was higher than that of T phase, which was related to the polarization rotation. When the temperature approached to the depolarization temperature, tetragonal macrodomains converted to microdomains. The polarization change led to the analogous observed in the plots of temperature-dependent pyroelectric coefficients and dielectric constants. However, the temperature-dependent remanent polarization indicated a lower O-T phase transition temperature. Such a discrepancy in Ta could be ascribed to the decline of ferroelectric phase transition energy caused by the superposition of the AC field at each temperature test point when perform bipolar ferroelectric hysteresis loops measuring. The domain structure variation upon heating an unpoled [0 0 1]-oriented 19PIN-45PMN-36PT single crystal was observed with a polarized light microscopy, further indicating the occurrence of the two phase transitions. (C) 2015 Elsevier Ltd. All rights reserved.