In this work, single-phase PFN ceramics that combine electrocaloric (EC) and magnetocaloric (MC) properties were successfully prepared. Electrical conductivity plays a crucial role in material’s EC cooling ability, therefore, in the first part, the influence of sintering conditions on electrical conductivity and consequently on EC properties of PFN were investigated. The conductivity was successfully suppressed with a proper optimization of the sintering conditions, whereby the sample sintered at 1000 °C exhibits the best properties, i.e., high density and the lowest specific electrical conductivity. The maximum values of ?Teff and ?TMC of this sample are 0.88 °C at 28 °C (100 kV·cm-1) and 0.14 °C at -271 °C (50 kOe), respectively. At higher sintering temperature, PbO starts to concentrate at the grain boundaries, which results in increased electrical conductivity of the material and leads to the appearance of Joule heating. EC as well as MC properties of PFN were further improved by doping with manganese. A smaller amount of dopant, i.e., 0.5 mol%, successfully suppresses the conductivity even at higher temperatures, leading to superior EC properties of 2.47 °C at 80 °C and 140 kV·cm-1. At the same time, the MC properties of the material are improved, resulting in ?TMC of 0.44 °C at -271 °C and 50 kOe. Both caloric values are approximately three times higher than the ones of undoped PFN.
COBISS.SI-ID: 32459303
We have prepared BFO ceramics and we investigated its electrical conductivity. We have found that if ceramics are prepared in a special way, by quenching, lower electrical conductivity is observed on the ferroelectric domain walls.
COBISS.SI-ID: 33296423
In this work, PFN–100xBFO (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5) solid solutions were successfully prepared by mechanochemical synthesis followed by sintering at different temperatures. An optimized processing procedure resulted in the preparation of highly dense single-phase ceramics with comparable grain size and relatively low dielectric losses, which enable the systematic study of dielectric, ferroelectric and electromechanical properties of the PFN–BFO solid solutions.
COBISS.SI-ID: 33157415