title: Size effects in a relaxor: further insights into PMN.
abstract: Dielectric measurements of PbMg1/3Nb2/3O3 (PMN) powder and dense ceramics with grain sizes between 15 nm and two microns were carried out in a broad frequency range (20 Hz-1 GHz). Clear grain size dependence of relaxor behavior was evidenced. A progressive transformation from Vogel-Fulcher behavior towards the Arrhenius process in the PMN with reduction of grain size in both ceramics and powder was observed. In the case of ceramics we were able to extract deeper information from the distributions of relaxation times and an analysis using the Vogel-Fulcher law, revealing two main contributions: a fast part of distribution of relaxation times with a maximum close to 10(-11) s, which is almost grain-size independent and has a non-polar origin; whereas, a process with long relaxation times (in the time range of 10(-8) to 10(-5) s) is associated with the dynamics of the polar nanoregions and is strongly suppressed with reduction of grain size. The results of dielectric investigations are confirmed by Nuclear Magnetic Resonance experiments.
authors.affiliation: Laboratory of Microwave Spectroscopy, Faculty of Physics, Vilnius University, 9 Sauletekio str., 10222 Vilnius, Lithuania.
authors.forename: R
authors.initials: R
authors.lastname: Grigalaitis
authors.forename: M
authors.initials: M
authors.lastname: Ivanov
authors.forename: J
authors.initials: J
authors.lastname: Macutkevic
authors.forename: J
authors.initials: J
authors.lastname: Banys
authors.forename: J
authors.initials: J
authors.lastname: Carreaud
authors.forename: J M
authors.initials: JM
authors.lastname: Kiat
authors.forename: V V
authors.initials: VV
authors.lastname: Laguta
authors.forename: B
authors.initials: B
authors.lastname: Zalar
mesh_terms: D003198:Computer Simulation; D017097:Electric Impedance; D004574:Electromagnetic Fields; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry*; D008956:Models, Chemical; D009556:Niobium; D010087:Oxides; D055672:Static Electricity
chemical_list: D010087:Oxides; C404734:lead magnesium niobate; D009556:Niobium