Relaxor behavior of CaxBa1−xNb2O6(0.18≤x≤0.35) tuned by Ca/Ba ratio and investigated by resonant ultrasound spectroscopy

Dependence of relaxor behavior of incompletely filled tetragonal tungsten bronze uniaxial relaxor ferroelectric calcium barium niobate (Ca${}_{x}$Ba${}_{1\ensuremath{-}x}$Nb${}_{2}$O${}_{6}$, CBN-$x$) on its composition was investigated by varying Ca/Ba ratio (0.18 \ensuremath{\le} $x$ \ensuremath{\le} 0.35) and studying its thermal and elastic properties. Recently, we have reported the relaxor behavior CBN-28 with the evidence of the existence of the Burns temperature ${T}_{\mathrm{B}}$, and the intermediate characteristic temperature ${T}^{*}$ [Pandey et al., Phys. Rev. B 84, 174102 (2011)]. In this work, we show that the dynamics of polar nanoregions (and hence the relaxor behavior) strongly varies with the Ca/Ba ratio. Evidence is found for a more pronounced relaxor behavior with increasing $x$. The Curie temperature and the Burns temperature are also very sensitive to the composition, whereas the characteristic temperature ${T}^{*}$ appears unaffected from the Ca/Ba ratio. The bonding interaction has been explained on the basis of bulk modulus, Poisson's ratio, and deviation from Cauchy relations. Presented results open the perspective to understand the variation of relaxor behavior of CBN-$x$ $(\ensuremath{\sim}0.18\ensuremath{\le}x\ensuremath{\le}\ensuremath{\sim}0.35)$ above Curie temperature.