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Abstract: Ferroelectric strontium barium niobate (SBN) powder was synthesized by solid-state route. The green compacts were sintered in the temperature range 1250–1350°C in a microwave furnace. The microstructural study, using SEM, revealed the grain size in the range 2–20μm without microcracks, depending on the sintering temperature. This is in contrast to that obtained conventionally for sintered SBN powder synthesized by solid-state route, which resulted in duplex microstructure with microcracks [N.S. VanDamme, A.E. Sutherland, L. Jones, K. Bridger, S.R. Winzer, J. Am. Ceram. Soc. 74 (1991) 1785; P.K. Patro, A.R. Kulkarni, C.S. Harendranath, Ceram. Int. 30 (2004) 1405; P.K. Patro, Trans. Ind. Inst. Metals 59 (2006) 229]. Impedance analyzer and ferroelectric hysteresis loop tracer were used for the dielectric, ferroelectric, I–V and electric fatigue measurements. Microwave sintering also resulted in a dielectric maxima ε max 2590 at 1kHz (compared to 1103 for conventional sintering [P.K. Patro, A.R. Kulkarni, C.S. Harendranath, Ceram. Int. 30 (2004) 1405]) for the sintering temperature of 1350°C. Similar improvement in microwave-sintered SBN was observed depending on their sintering condition. The origin of this difference is attributed to microstructural differences arising from difference in heating method. In this paper the observed dielectric and ferroelectric behavior have been correlated with different sintering conditions and consequent microstructure due to microwave sintering. [Copyright &y& Elsevier]

Abstract: Strontium barium niobate (SBN) ceramics, synthesized through partial co-precipitation, was sintered at—6, 12 and 24h, respectively, at 1250, 1300 and 1350°C. Structural developments, developments in porosity, grain size, residual stress and crystallographic texture and its effect on dielectric constants were studied at different sintering conditions. The bulk crystallographic texture was largely unaffected by the sintering conditions used, though all other structural parameters evolved through sintering schedule. An effort was made to relate the changes in dielectric constant with the changes in structural parameters. Normal grain growth or changes in residual stress pattern either had relatively insignificant effects on dielectric constant or decoupling the relative effects was difficult from the present set of data. On the other hand, the strongest increase in dielectric constant was achieved through reduced porosity/defects, while abnormal growth caused the largest drop. [Copyright &y& Elsevier]

In the present study, two different sets of precursors have been used in the synthesis of strontium barium niobate (SBN50) by conventional solid-state route: I. Sr(NO3)2, Ba(NO3)2, Nb2O5 and II. SrCO3, BaCO3 and Nb2O5. The formation of SBN50 phase was completed at 1150 °C. The green compacts, of the calcined powder, were sintered at temperatures varying from 1250 to 1350 °C. Microstructural characterization was done using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The aim was to study the dielectric and ferroelectric behavior depending on the precursors used and the sintering conditions and correlate with microstructure. The synthesis, involving the precursor set-I, showed a duplex microstructure with large number of small grains, of size 10–15 μm, sandwiched between very large grains, of size in the range of 50–200 μm. On the other hand the second set of precursor resulted in a microstructure devoid of duplex nature. The microstructure consisted of polyhedral grains having more or less uniform size. SBN from set-II showed a better dielectric property compared to set-I. The discrepancies in this ferroelectric/dielectric behavior, have been explained in terms of density as well as microstructural differences. [Copyright &y& Elsevier]

Strontium Barium Niobate, Sr0.5Ba0.5Nb2O6 (SBN50), has been synthesized, for the first time, by partial coprecipitation of SrCl2 and BaCl2 on Nb2O5. Powder X-ray diffraction study shows tetragonal tungsten bronze phase formation at 1200 °C. Particle morphology and size of calcined powder has been examined using Transmission Electron Microscopy. The particle size of calcined powder ranges between 250 and 300 nm. The green compacts have been sintered at 1250, 1300 and 1350 °C and at each temperature for 6, 12 and 24 h, respectively. Effect of sintering time and temperature on dielectric properties has been investigated. Scanning electron microscopy has been used for grain morphology studies. Grains have been found to be tetragonal in shape and show variation in size for different sintering conditions. Highest dielectric constant (ϵ) has been observed for the pellet sintered at 1350 °C for 6 h. A variation in Tc from 93 to 119 °C has also been observed. [Copyright &y& Elsevier]

We have performed magnetic and transport measurements on La[sub 0.67]Ca[sub 0.33]MnO[sub 3] polycrystalline and partially melted samples. The magnetization and resistance decrease as sintering temperature is increased. The insulator-to-metal transition temperature is remarkably enhanced in the partially melted sample, enabling its possible applications at room temperature. The microscopic studies in melt samples show an excellent connectivity between grains, suggesting the enhancement of percolative transport by opening new conduction channels and the disappearance of magnetic phase boundary at elevated temperature by the ordering of Mn spins blocked at the grain boundary of sintered samples. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]