First principles study of hydrogen in lead zirconate titanate

Abstract

Lead zirconate titanate (PZT) is a widely used piezoelectric and ferroelectric material with applications ranging from actuators in fuel injectors to ferroelectric random-access memories. Hydrogen is known to cause degradation in most metals through a ductile-to-brittle transformation called hydrogen embrittlement. Similarly, piezoelectric materials have also been found to degrade through hydrogen exposure, not only due to embrittlement, but also through reduced polarity and Pb migration. This gives rise to the need of understanding the behavior of hydrogen in piezoelectric material. This research presents the initial results of a study which aims to simulate hydrogen diffusion in PZT using multi-scale simulation techniques. First-principles calculations were done to determine the possible hydrogen occupancy locations in the PZT lattice. For these locations we calculated the effect on polarization and the dimensions of the PZT lattice by dissolved hydrogen and predicting paths available for the escape of hydrogen atoms. These results will serve as a basis for future nudged elastic band calculations to determine the diffusion characteristics for the individual diffusion steps, which can in turn be used to predict the bulk diffusion characteristics with kinetic Monte Carlo simulations.

Unraveling Discharge and Surface Mechanisms in Plasma-Assisted Ammonia Reactions

“…For example, it is the most likely that under our experimental conditions the initial rupture of the ammonia (processes and ) and deuterium molecules, which are the rate-limiting step for the detected exchange processes, mainly occurs by electron impact (eq ) and, possibly, through dissociative surface adsorption. In this regard, as recently proposed by Hong et al, it is noteworthy that although we do not use any metal catalyst where dihydrogen might readily adsorb and dissociate, this is a likely process on PZT ,, that might be very important in atmospheric pressure plasma processes. Under our working conditions, this would be an important route for the hydrogen/deuterium incorporation in PZT as discussed in the next section.…”

“…Under these conditions, direct interaction of PZT with H*­(D*) radicals and possibly molecular hydrogen and other excited molecular species of dihydrogen should promote the incorporation of H­(D) onto the surface (e.g., in the form of −OH/D groups) and likely also the interior of the PZT pellets. Although the mechanism and better conditions for such a hydrogen plasma-driven incorporation process and its mobilization upon interaction with a plasma of hydrogen are still unknown, it is noteworthy that large amounts of atomic hydrogen incorporation are known to occur in PZT treated thermally with hydrogen or activated electrochemically with a Pt electrode in a water solution. , According to these and other works in the literature, the capacity of PZT to incorporate hydrogen is very high and can amount to one atom per lattice octahedral unit of its structure (maximum 1H:1Pb ratio). , …”

“…We refer to the direct involvement of the surface of the moderator material in the reaction mechanisms. With this purpose, we studied the N 2 + D 2 and N 2 + H 2 plasma reactions, the latter after prolonged exposure of the interelectrode material (i.e., lead zirconate titanatePZTa material known for its high ability to incorporate hydrogen in its structure − ) to a D 2 plasma and followed the H/D isotope distribution in the produced ammonia. The isotope-exchange results together with the analysis of the optical emission spectra from intermediate species formed in the plasma have permitted unraveling the basic reaction mechanisms both in the plasma and at the surface of the interelectrode material and established the role of intermediate plasma species in the plasma synthesis/decomposition of ammonia.…”

Low cost, contamination-free, and damage-free fabrication of PZT MEMS on SOI substrate

“…The high-temperature processing and hydrogen content of PECVD SiO 2 deposition is detrimental to both the remnant polarisation and the effective coupling coefficient of PZT thin film. The process-induced damage to ferroelectric thin films has been studied extensively [28,[35][36][37][38][39][40][41]. Han and Ma [35] investigated the dependence of electrode material on hydrogen-induced damage in PZT thin films.…”

Numerical simulations of hydrogen interstitial diffusion and ferroelectricity degradation in lead titanate films

“…Most previous studies about hydrogen impurities in ferroelectric materials are from experiments [21][22][23]. There are a few computational works based on density functional theory (DFT) calculations, but the system sizes were limited [24][25][26][27]. In this work, we present a computational model that predicts the ferroelectric properties of PTO films with various hydrogen diffusion conditions.…”