Ultrabroadband dielectric spectroscopy and phonons in (Pb1-x/2Lax)(Zr0.9Ti0.1)O3

The dielectric behavior of (Pb1-x/2Lax) (Zr0.9Ti0.1)O-3 PLZT 100x/90/10 (0 <= 100x <= 1) was studied in the frequency range 10(2)-10(14) Hz using dielectric, time-domain terahertz (THz), far-infrared, and Raman spectroscopy in the temperature interval 10-900 K. PZT 90/10 and PLZT 2/90/10 undergo two phase transitions, from a cubic paraelectric to a rhombohedral untilted ferroelectric (FE) phase and on further cooling to a tilted FE phase. PLZT 4/90/10 and PLZT 10/90/10 are incommensurately modulated and composed of an intergrowth of polar and antipolar cation displacements. These samples consequently demonstrate a FE soft mode which exhibits minimal frequency several tens of degrees above the nominal antiferroelectric phase transition temperature. The dielectric response of PLZT 100x/90/10 is mainly governed by a gigahertz relaxation and a soft phonon component in the THz range. As in other PbO-based perovskites, the soft mode is split into a higher-frequency component (omega similar to 80 cm(-1)) and a highly damped THz component (omega similar to 30 cm(-1)), with larger dielectric strength already in the paraelectric phase. (C) 2010 American Institute of Physics. [doi:10.1063/1.3501105]