Electronic transitions and dielectric functions of relaxor ferroelectric Pb(In_(1/2)Nb_(1/2))O_3-Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 single crystals: Temperature dependent spectroscopic study

摘要

Optical properties and phase transitions of Pb(In_(1/2)Nb_(1/2))O_3-Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 (PIN-PMN-PT) crystals near morphotropic phase boundary (MPB) have been investigated by temperature dependent transmittance and reflectance spectra. Three critical point energies E_g ＝ 3.17-3.18 eV, E_a ＝ 3.41-3.61 eV, and E_b ＝ 4.74-4.81 eV can be assigned to the transitions from oxygen 2p to titanium d, niobium d, and lead 6p states, respectively. They show narrowing trends with increasing temperature, which can be caused by thermal expansion of the lattice and electron-phonon interaction. Deviation from the linear behaviors can be observed from E_a and E_b versus PT concentration, indicating a complex multiphase structure near MPB region.