Polarization Switching of and Electron Emission from Lead Lanthanum Zirconate Titanate Ceramics

Abstract

This paper focuses on understanding the influence of material properties on the complicated ferroelectric (FE) emission process. Three different compositions in the lead lanthanum zirconate titanate (PLZT) system were chosen for study, based on their widely different dielectric and ferroelectric properties: antiferroelectric (AFE) 2/95/5, "normal" ferroelectric 8/65/35, and nonferroelectric 15/65/35. Repeatable emission was obtained from the 2/95/5 composition, which could also be modulated at high frequency (200 kHz). The fast AFE → ← FE phase transition is responsible for the FE emission properties of this material, which is supported by the relationship between the switching current and the emission current. Comparatively, FE emission from the 8/65/35 composition degraded rapidly, which was attributed to decreases in the remanent polarization. No emission signal was detected from the 15/65/35 composition, because no switching activity occurs, which can be interpreted as additional evidence that electron emission from the previously mentioned two compositions was indeed a FE emission process.

A- and B-compensated PLZT x/90/10: Sintering and microstructural analysis

“…A dielectric permittivity of 6400 at a maximum temperature of 210 • C is reported for the antiferroelectric PLZT phase with the composition 2/95/5. 32 The information regarding the A-or B-compensation models in PLZT available in the open literature is scattered and the fundamental question what is the influence of excess charge in PLZT, which originates from the addition of La 3+ to the Pb 2+ crystallographic sites, on the sintering behavior and microstructure, remain. The authors would like to stress that various authors have prepared either A-or B-compensated PLZT at various processing conditions therefore it is unlikely to compare the microstructural characteristics of PLZT prepared at non-identical sintering temperatures, times or atmospheres.…”

Electron Emission from Barium Strontium Titanate Ceramics

“…These results are different from other groups' results. Most results of other groups who reported ferroelectric emission 5 or plasma emission 11–13 have shown only one emission pulse per triggering voltage. Only Zhang and Huebner 6 reported two sharp emission pulses, which were 200–500 ns apart from each other.…”

“…A ferroelectric material that has been polarized will have a net positive surface charge that attracts compensating electrons to preserve charge neutrality. When fast reversal of the polarization occurs, the negative charges of the ferroelectric dipoles orient toward the emitting surface, which effectively creates a repulsive force on the surface electrons and thereby emitting them 5–9 . Recently, it was reported that high electron emission was observed in the paraelectric phase ferroelectrics and it was pointed out that the electrons are emitted from surface plasma initiated at the metal–dielectric boundary 10–13 .…”

Electron emission from La-doped Pb(Zr,Sn,Ti)O3 anti-ferroelectrics by pulse electric field and the relevant physical mechanism

“…Strong electron emission from antiferroelectric ceramics has already been reported and ascribed to the phase transition induced by a strong pulse electric field [4,9,12,13] . Based on the above experimental results, here we argue that domain movement near triple junction under the application of triggering voltage pulse may be responsible for the emission from PLZST samples.…”

“…In 1989, Gundel et al [2] reported an emission beam current density of more than 100 A/cm 2 using lead zirconate titanate (PZT) and lanthanum-doped lead zirconate titanate (PLZT) as cathode materials in the absence of any external extraction field, and this was later confirmed by many groups. Since then ferroelectric cathodes have been widely investigated by researchers all over the world [3][4][5][6][7][8][9] . In spite of much effort had been devoted to this topic, the possible mechanisms involved in the ferroelectric emission have not yet been completely elucidated.…”