Model for the cold sintering of lead zirconate titanate ceramic composites

Abstract

AbstractA model was developed to describe the cold sintering process (CSP) of lead zirconate titanate (PZT) using moistened lead nitrate as a sintering aid. The densities of PZT powder with different volume fractions of lead nitrate were evaluated after cold sintering at 300°C and 500 MPa for 3 hours. The densities were categorized into three zones. In zone I, the relative density following cold sintering increases from 66% to 80%, as the lead nitrate contents rise from 0 to 14 vol%. In this case, the lead nitrate acts to fill some of the pore volume between PZT grains. Zone II serves as a transition region, where there is both pore filling and dilution of the PZT grains associated with lead nitrate contents from 14 to 34 vol%. In zone III, the relative density drops due to dilution at lead nitrate contents exceeding 34 vol%. To slow the process down so that the kinetics could be studied more readily, samples were cold sintered at room‐temperature and 500 MPa. It was found that during the first few seconds of compaction, 85PZT/15Pb(NO3)2 rapidly densified from 51% to 61% relative density due to particle re‐arrangement. For longer times at pressure, the CSP improved the packing relative to PZT compacted without the lead nitrate, yielding a higher relative density. The late stages of the PZT/Pb(NO3)2 CSP could be well described using a viscous sintering model for pressures from 50 MPa to 1000 MPa and temperatures from 25°C to 300°C.