J. Handerek

Copious electron emission from PLZT ceramics with a high zirconium concentration

Abstract We describe the experimental method and report the results of electron emission from PLZT-2/95/5 ceramics subjected to rectangular HV pulses. The influence of HV amplitude, of gas pressure, and of temperature on electron beam current-density and charge was investigated. The kinetic energy was estimated by applying a decelerating field. Emitted current-density pulses of several A/cm2 and charges of 1 μC/cm2 are measured. A tentative interpretation is given.

Low‐pressure hollow cathode switch triggered by a pulsed electron beam emitted from ferroelectrics

A new type of low‐pressure gas switch is described. The switch is triggered by an electron beam that is emitted from the surface of a ferroelectric sample. The electron beam is generated within the hollow cathode and ejected through a hole of arbitrary shape into the main gap of the switch. The beam current and the electron energy can be chosen such that breakdown is achieved with small jitter. The switch with its ferroelectric trigger requires neither heating nor an auxiliary gas discharge. The fast spontaneous polarization change ΔPs, which is the cause of electron emission, is induced by a high‐voltage pulse from an electronic switching circuit.

Dielectric and pyroelectric properties of (Pb1-xBax)(Zr0.70Ti0.30) O3 [x=0.25÷0.35] ceramics exhibiting the relaxor ferroelectrics behaviour

Dielectric constant, loss factor and remanent polarization were investigated as a function of temperature for PBZT - type ceramics with Zr/Ti ratio equal 70/30 and Ba contents x = 0.25÷-0.35. Additionally measurements of pyroelectric and thermally stimulated depolarization currents were carried out. The reported experimental results obtained reveal the relaxor ferroelectrics behaviour of the studied ceramics. The physical processes leading to the relaxor behaviour are discussed in this paper. The Bi-doped PBZT ceramics were also investigated. A small amount of this dopant caused considerable improvement in the quality of the ceramics and their relaxor behaviour.

Pulsed electron emission from PLZT ceramics

Abstract New experimental results on electron emission from PLZT ceramics of composition 2/95/5, subjected to rectangular high-voltage pulses are reported. The dependence of the emitted electron charge on the electric field strength and temperature was investigated. The energy of the emitted electrons was estimated by applying a decelerating potential to an auxiliary grid electrode. Emitted current densities of several A/cm2 and emitted charges up to ∼ 1 μC/cm2 (∼1013 electrons/cm2) were observed.

Intense laser‐induced electron emission from prepoled lead‐lanthanum‐zirconium‐titanate ceramics

A sample of lead‐lanthanum‐zirconium‐titanate (PLZT 9/65/35) has been exposed to 6‐ns‐long laser pulses of 266 nm wavelength. The maximum output pulse energy of the laser beam was 300 μJ, the output power density on the sample 5×105 W/cm2, and the beam diameter 3 mm. By applying a moderate extraction voltage of several kilovolts, intense electron beam pulses are emitted from the free sample surface. Their time structure corresponds to the time structure of the laser pulse. Electron beam current intensities of up to 0.1 A and 2 A/cm2 and total charges of 1 nC (corresponding to 20 nC/cm2 ) were measured with a simple Faraday cup. In the range where the parameters of laser intensity and of extraction voltage could be varied their influence on the emitted electron beam current amplitude was determined.

The first evidence of two phase transitions in PbZrO3 crystals derived from simultaneous raman and dielectric measurements

Abstract The temperature dependence of Raman scattering near the phase transition points between antiferroelectric orthorhombic(Aa), ferroelectric rhombohedral (FR) and paraelectric cubic (PC) phases was investigated in PbZrO3 crystals. The measurements were carried out with simultaneous observations of the electric permittivity along the [111] direction. The ferroelectric nature of the intermediate phase had previously been observed by the hysteresis loop and pyroelectric tests. The evolution of the Raman spectra from Aa to Pc through the FR phase is reported. The main modification of the Raman spectrum takes place at the temperature at which e(T) begins to exhibit significant variations.

Phase transitions in Nb-doped Pb(Zr0.95Ti0.05)O3 ceramics investigated by dielectric, pyroelectric and Raman scattering measurements

Abstract Dielectric and other complementary measurements were carried out in order to confirm the AO-FR(LT)-FR(HT)-PC phase sequence and to determine the temperatures of each phase transition occurring in undoped PZT ceramics with Zr/Ti ratio 95/5 and Nb-doped ceramics with 0.25 ÷ 1 weight % of Nb2O5. These measurements revealed the diffused character of particular phase transitions and especially of the AO-FR(LT) one. The AO-FR(LT) and FR(LT)-FR(HT) phase transitions occur only in the part of sample volume in the vicinities of the determined temperatures of these transitions and the first one is extremaly broadened and extended towards the low temperatures in the remaining volume of the crystal. Temperature evolution of Raman spectra and the central peak revealed changes of the structure, frequencies and intensity of the scattered light in each phase transition.

The influence of an electric field on the DPT in Pb (Zr1−XTi1−X)O3 (x≤0.05)

Abstract In Pb(Zr1−XTiX)O3 for Ti content x>xc ≃ 0.03, a marked increase of the derivatives (dTFA/dE) was detected. X-ray investigations of the volume content of neighbouring phases in the vicinity of phase transition temperatures shoved that for samples with Ti content x>xc the temperature range of coexistence of the antiferroelectric and ferroelectric phases is notably broadened.

A robust and powerful green light photoemission source: The ferroelectric ceramics

The photoemission characteristics of ceramic disks of lead zirconate titanate lanthanum doped (PLZT), have been investigated. We observe 1 nC of extracted charge under an accelerating field of 20 kV/cm in poor vacuum conditions. The emission is clearly limited by space charge effects. The extrapolated quantum efficiency results in ≈10−6. The yield of a PLZT ceramic in the ferroelectric state and its slope versus light intensity have turned out higher than those of antiferroelectric ceramic. Samples in different experimental configurations have shown different nonlinear yields.

The intermediate ferroelectric phase in PbZrOa with high concentration of defects

Abstract Data is presented on the influence of a d.c. electric field on the temperature dependence of electric permittivity and remanent polarization in PbZrO3 ceramic samples with high concentration of point defects arising during the technological process and formed additionally by heating in a vacuum.