Phase transitions in LixAg1−x(Nb0.5Ta0.5)O3 solid solutions

Abstract

Li x Ag 1 − x ( Nb 0.5 Ta 0.5 ) O 3 (0≤x≤0.25) solid solutions have been fabricated by the mixed oxide method. Compositions with x≤0.15 were single phase perovskite by x-ray diffraction (XRD) and could be indexed using the end member, Ag(Nb0.5Ta0.5)O3 Pbcm cell, 2a,2a,4a (where a is the pseudocubic lattice parameter). For x≥0.20, Li(Nb,Ta)O3 peaks emerged as a second phase. Electron diffraction patterns from the perovskite phase could also be indexed according to the Pbcm cell but there was a systematic decrease in the intensity of {0014}p as Li concentration increased which indicated that the correlation length of cation displacements perpendicular to c decreased from long to short range order. The reduction in correlation length of cation displacements resulted in a convergence of the M1-M2-M3 transitions to give a single broad, frequency dependent maximum at x=0.15. Further increase in Li concentration did not qualitatively affect the temperature dependent dielectric data, consistent with the solubility limit determined by XRD. P-E loops did not show any significant enhancement in switchable polarization in the system with the majority of samples exhibiting a linear dielectric response.