Browsing by Author "Ranjan, R"

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    Interplay of local polarization, ionic size, and octahedral tilt in SrTiO3-Na0.5Bi0.5TiO3
    (American Physical Society (APS), 2024-01-01) Sharma, D; Punetha, P; Adhikary, GD; Avdeev, M; Ranjan, R
    We show that the ferroelectric system (1−x) SrTiO3−(x) Na0.5Bi0.5TiO3 exhibits an interesting interplay of local polarization, ionic size effect, and octahedral tilt. This interplay results in (i) a nonmonotonic composition dependence of the lattice volume at room temperature and (ii) existence of a unique temperature (300∘C) at which the competing effects of electrostriction caused by the formation of polar nanoregions and geometrical ionic size make the system exhibit composition independent lattice parameters in a large composition interval x<0.40. ©2024 American Physical Society.
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    Phase boundary at x=0.03 and its anomalous influence on the structure and properties in the lead-free piezoelectric (1−x)Na1/2Bi1/2TiO3−(x)BaTiO3
    (American Physical Society, 2015-12-14) Rao, BN; Avdeev, M; Kennedy, BJ; Ranjan, R
    The complexity associated with local structures continues to pose challenges with regard to the understanding of the structure-property relationship in Na1/2Bi1/2TiO3-based lead-free piezoceramics. (1−x)Na1/2Bi1/2TiO3−(x)BaTiO3 is an extensively studied system because of its interesting piezoelectric properties. Recently, a room temperature phase boundary was reported at x=0.03 in this system [Ma et al., Adv. Funct. Mater. 23, 5261 (2013)]. In the present work we have examined this subtle phase boundary using x-ray diffraction, neutron diffraction, dielectric measurements as a function of composition (x<0.06), temperature, and electric field. Our results show that this boundary separates an R3c+Cc-like structural state for x<0.03 from an R3c+ cubiclike structural state for 0.03≤x≤0.05 in the unpoled specimens. This phase boundary is characterized by an anomalous reduction in the depolarization temperature, and a suppression of the tetragonal distortion of the high temperature P4bm phase. Our results also provide the clue to understand the pathway leading to the cubiclike structure of the critical composition x=0.06, known for its highest piezoelectric response. ©2015 American Physical Society