Synthesis and thermal expansion hysteresis of Ca1-xSrxZr4P6O24

The low thermal expansion ceramic system, Ca1-xSrxZr4P6O24, for the compositions with x = 0, 0.25, 0.50, 0.75 and 1 was synthesized by solid-state reaction. The sintering characteristics were ascertained by bulk density measurements. The fracture surface microstructure examined by scanning electron microscopy showed the average grain size of 2.47 mum for all the compositions. The thermal expansion data for these ceramic systems over the temperature range 25-800degreesC is reported. The sinterability of various solid solutions and the hysteresis in dilatometric behaviour are shown to be related to the crystallographic thermal expansion anisotropy. A steady increase in the amount of porosity and critical grain size with increase in x is suggested to explain the observed decrease in the hysteresis

Ac conductivity studies on the Li irradiated PZT and SBT ferroelectric thin films

Pb(Zr_{0}_{.53}Ti_{0}_{.47})O_{3 }(PZT) and $SrBi_{2}Ta_{2}O_{9 }$(SBT) ferroelectric thin films were prepared on Pt coated Si substrates by pulsed laser ablation technique and their responses to the high energy Lithium ion irradiation were studied in terms of their ac conductivity, dielectric studies, polarization hysteresis and structural properties. The PZT and SBT thin films were fabricated in Metal/ Insulator-Metal capacitor configuration and were irradiated with the 50 MeV Lithium ions with varying fluence from $1*10^{12}$ to $1-10^{14}$ions cm^-^2. The ferroelectric properties were observed to be degraded by the irradiation. The ac conductivity of the films was explained by the charge carrier hopping model. Irradiated PZT thin films exhibited a significant variation on the frequency dependent exponent(s) while the irradiated SBT thin films had a negligible influence. The activation energy calculated from the Arrhenius plots was found to increase from 1.05 to 1.55 eV for PZT and from 0.85 to 0.91 eV for SBT thin film after irradiation. These energies were attributed to the oxygen vacancies and the deep trap carriers induced by the irradiation

Radiation resistance of PFN and PNM-PT relaxor ferroelectrics

The relaxor ferroelectric compositions Pb(Fe1/2Nb1/2)O-3 (PEN) and [Pb(Mg1/3Nb2/3)O-3](0.8)-[PbTiO3](0.2) (PMN-PT) are studied for their radiation response to the high energy heavy ions (50 MeV Li3+, fluence 1 X 10(13)-1 X 10(14) ions/cm(2)) in terms of their structural, dielectric and piezoelectric properties. There was no change in the crystallinity of both the compositions after irradiation as seen from the XRD. The PEN composition did not show much change in the dielectric constant but the value of T-m decreased by 8degreesC. The PMN-PT composition showed an increase in the dielectric constant with increase in the irradiation fluence from 1 x 10(13) to 1 X 10(14) ions/cm(2) with no change in the value of T-m. The piezoelectric coefficient decreased in both the samples after irradiation. Among the compositions studied, PEN is observed to be more radiation resistant to changes in structural and dielectric properties than PM-PT. (C) 2003 Elsevier Ltd. All rights reserved

High Energy Oxygen Ion Induced Modifications in Ferroelectric SrBi2Ta2O9SrBi_{2}Ta_{2}O_{9} Thin Films

The effects of high energy oxygen ion irradiation on the ferroelectric properties of $SrBi_{2}Ta_{2}O_{9}$ (SBT) thin films are reported. The films were grown using pulsed laser ablation. Fluence dependant degradation in the ferroelectric properties was observed. The dielectric constant did not show any frequency dispersion in both the unirradiated and irradiated films. After irradiation, the films showed only a decrease in the capacitance value retaining their ferroelectric nature. The switching voltages increased with broader peaks and showed a partial recovery after annealing of the irradiated film. A slim hysteresis loop with decreased $P_{s}$, $P_{r}$ and $E_{c}$ values was observed. The current density increased to a larger extent. The decrease in the dielectric constant, capacitance and polarization values was to a lesser extent as compared to those of PZT thin films under identical irradiation conditions. The results presented in this paper are illustrative of the fact that the layered perovskites have a stable structure and are less sensitive to extrinsic effects. The relatively high resistance of bismuth layered perovskites such as SBT to the high energy radiation along with the greater fatigue endurance as compared to PZT make them better candidates for applications in memory devices

50 MeV Li3+ irradiation effects on the thermal expansion of Ca1âxSrxZr4P6O24

The influence of 50 MeV Li3+ ion irradiation on the thermal expansion of the low thermal expansion ceramic Ca1-xSrxZr4P6O24 (x = 0.00, 0.25,0.50, 0.75 and 1.00) belonging to the sodium zirconium phosphate (NZP) family of ceramics was studied in the temperature range 300-1100 K. The observed changes in XRD, microstructure and thermal expansion are reported. These changes are strongly ependent upon the strontium substitution at calcium sites in the basic structure, The XRD and scanning electron microscope (SEM) studies indicate that the ion irradiation causes morphization, especially at the grain boundaries. The hermal expansion hysteresis reduces due to Sr substitution and is further reduced upon irradiation. It is suggested that the amorphization due to irradiation helped release of thermal stress and thereby lead to the reduction in the hysteresis in thermal expansion. The composition with x = 0.50 having low coefficient of thermal expansion (CTE), low hysteresis and the least thermal expansion anisotropy is least affected by the Li3+ irradiation and hence may qualify as the radiation resistant material

50 MeV Li3+Li^{3+} irradiation effects on the thermal expansion of Ca1−xSrxZr4P6O24Ca_{1-x}Sr{_x}Zr{_4}P{_6}O_{24}

The influence of 50 MeV Li3+ ion irradiation on the thermal expansion of the low thermal expansion ceramic Ca1-xSrxZr4P6O24 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) belonging to the sodium zirconium phosphate (NZP) family of ceramics was studied in the temperature range 300-1100 K. The observed changes in XRD, microstructure and thermal expansion are reported. These changes are strongly dependent upon the strontium substitution at calcium sites in the basic structure, The XRD and scanning electron microscope (SEM) studies indicate that the ion irradiation causes amorphization, especially at the grain boundaries. The thermal expansion hysteresis reduces due to Sr substitution and is further reduced upon irradiation. It is suggested that the amorphization due to irradiation helped release of thermal stress and thereby lead to the reduction in the hysteresis in thermal expansion. The composition with x = 0.50 having low coefficient of thermal expansion (CTE), low hysteresis and the least thermal expansion anisotropy is least affected by the Li3+ irradiation and hence may qualify as the radiation resistant material. (C) 2002 Elsevier Science B.V. All rights reserved