PbMg _1/3 Nb _2/3 O₃ dielectric aging in the freezing temperature region

Aging of the relaxors and PbMgNbO3 in particular was extensively studied in last two decades. Most of the results were related to the low temperature glass-like region. No systematic data around the freezing temperatures were reported. To cover this still missing information we have studied the evolution of the dielectric spectra in the broad frequency region from 10(-1) Hz to 10(6) Hz both below and above the freezing temperature 240 K. Below freezing temperature the existence of the earlier reported waiting time-frequency scaling at frequencies below approximate to 50 Hz is confirmed. At higher frequencies this deviation from the scaling is observed that can be tentatively attributed to the complexity of the relaxing entities. Above T-f aging is observed only in the restricted frequency interval below the maximum of the dielectric loss spectrum. The observed effect can be attributed to the hardening and narrowing of the dielectric loss spectra and decreasing of the dielectric strength with time. The explanation is proposed based on the concept of the creation of the degenerate polar nanoregions covering several chemically ordered regions (COR) (multi PNRs-MPNRs). These MPNRs are large compare to the PNRs located at the single CORs and some of them may become frozen resulting in the described spectra changes.