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K0.5Bi0.5TiO3 ceramics with cuboid (KBT-C), rod (KBT-R), and plate (KBT-P)-shaped grainswere fabricated via solid-state reaction and reactive template grain growth (using K2Ti6O13 and K0.5Bi4.5Ti4O15) methods, and the strong dependence of electrical properties on the grain morphology was demonstrated. The average grain sizes of KBT-R, KBT-P, and KBT-C were ~30 ± 10 μm, 7 ± 1 μm, and 350 ± 50 nm, respectively. While the room temperature dielectric constant decreased for KBT-R (~240) and KBT-P (~230) from ~500 for KBT-C, a significant enhancement in the piezoelectric charge coefficient (d33) was noticed for KBT-R (~95 pC/N) and KBT-P (~105 pC/N) samples compared to that of KBT-C ceramic (~60 pC/N). Accordingly, a large improvement in piezoelectric voltage coefficient (g33) of almost 300% in poled KBT-R (~45 x 10-3 Vm/N) and 400% in KBT-P (~54 x 10-3 Vm/N) samples over the KBT-C ceramic was obtained. Interestingly, a significantly lower activation energy (Ea) for KBT-C (~0.71 eV) below the temperature of the dielectricmaximum (Tm) was noticed compared to KBT-R (~1.07 eV) and KBT-P (~1.00 eV), suggesting a strong dependence of DC conduction on grain morphology. Furthermore, chronoamperometry measurements confirmed amixed electronic and ionic conduction at higher temperatures in all samples. [ABSTRACT FROM AUTHOR]

The present study reveals the effect of LaScO3 content on the structural, dielectric, and piezoelectric properties of perovskite structured (1 − x)(K0.5Bi0.5)TiO3–xLaScO3 (named as KBT–LSO) (x = 0–0.40) ceramics. A decrease in tetragonality and an increase in cubic phase fraction with LaScO3 doping were observed in Rietveld refinement of synchrotron X-ray diffraction (SXRD) data. Room temperature dielectric constant (εr) was found to improve in KBT–LSO solid solution. A continuous decrement in temperature of dielectric maxima (Tm) from 360 °C for x = 0.00 to 87 °C for x = 0.40 of LSO-doped KBT sample (at 1 MHz) was noticed. Highly diffuse dielectric anomaly and increasing relaxor behavior were observed with increased LSO doping content. The greater value of depolarization temperature (Td ~ 310 °C) compared to normal to relaxor ferroelectric transition (TF-R ~ 255 °C) for a 2% LSO-doped sample signifies a nonergodic relaxor state in the system. The impedance spectroscopy suggested improved DC resistivity with LSO incorporation in KBT lattice. The activation energies were obtained in the ranges 0.98 ± 0.03 eV to 1.50 ± 0.02 eV using Arrhenius equations which signifies the reduction in oxygen vacancies due to LSO doping. The current (I)–voltage (V) plot confirmed the decrement in room temperature DC conductivity (σDC) with LSO doping concentration. [ABSTRACT FROM AUTHOR]

Developing solid electrolytes for all-solid-state lithium batteries with superior performance is crucial for portable energy storage. This study uses a traditional solid-state reaction technique to fabricate a NASICON-type medium entropy Li 1.5 Sn 1.0 Al 0.5 Zr 0.5 (PO 4) 3 (LSAZP) ceramic electrolyte. The Rietveld refinement of room temperature X-ray diffraction (XRD) data confirms a pure rhombohedral phase (R 3 ‾ c) for LSAZP ceramic sintered at 1050 °C. Temperature-dependent synchrotron XRD data demonstrates an increase in lattice parameter c with a positive coefficient of thermal expansion (+2.40 × 10−5 K−1) and a negative coefficient of thermal expansion (−1.26 × 10−6 K−1) for the lattice parameter a with increasing temperature. Interestingly, despite the anisotropic thermal expansion, no intergranular cracks, typically observed in rhombohedral NASICON-type phases, are noticeable in the scanning electron micrographs of the LSAZP samples. The sample sintered at 1050 °C (relative density ∼90 %) exhibits an excellent room temperature conductivity of ∼2.95 × 10−4 S cm−1 and activation energy ∼0.39 ± 0.02 eV. The Li-ion transference number is ∼0.99, suggesting that Li-ion is the dominant charge carrier in the sample. During galvanostatic lithium plating-stripping tests, the symmetric Li|LSAZP|Li cell demonstrates excellent lithium plating-stripping stability over 50 h at a current density of 4 μA cm−2. [Display omitted] • NASICON-type medium entropy Li 1.5 Sn 1.0 Al 0.5 Zr 0.5 (PO 4) 3 ceramics were fabricated. • Sample sintered at 1050 °C exhibited an exceptional RT conductivity of 2.95 × 10−4 S cm−1. • No microcracks were observed in sintered samples despite an anisotropic thermal expansion. [ABSTRACT FROM AUTHOR]