Cationic substitution engineering in GdInO3 at A-site: Insights into phase evolution and search for compositionally tailored relaxors.

The present work reports detailed structural and electrical studies on A-site substituted La x Gd 1-x InO 3 (0.0 ≤x ≤ 1.0) system with structurally different end members in search for tailored lead-free relaxors. The motivation is the possibility to manipulate the crystal structure to maneuver electrical properties in hexagonal GdInO 3 , a candidate for geometric ferroelectricity. The hybrid synthesis protocol involving gel-combustion led to stabilisation of metastable polymorphs in some nominal compositions due to kinetic stabilisation. Non-preference of La3+ for 7- fold coordinated A-site in hexagonal structure manifested in wide-ranging orthorhombic phase field prevailing even in Gd3+-rich region, also supported by theoretical studies. P-E studies on Gd3+-rich compositions exhibited hysteresis loop which suddenly became narrow for the nominal composition La 0.4 Gd 0.6 InO 3 with very low remanent polarisation. This along with broad maximum exhibited in plot of dielectric constant vs temperature that shifts to higher T upon increasing frequency, for La 0.4 Gd 0.6 InO 3 , supports presence of relaxor-type behavior. Signature of hexagonal-type vibrations in otherwise bulk orthorhombic (by XRD) La 0.4 Gd 0.6 InO 3 and anomalous trend in La/Gd vibrational mode along with narrowing down of Raman modes have been cited as plausible structural reasons for the relaxor behaviour. This has significance in context of structure-electrical property relationship leading to development of potential lead-free relaxors. [Display omitted] • Detailed phase evolution in GdInO 3 (P6 3 cm)- LaInO 3 (Pnma) with composition and T. • C-type metastable phases observed by synthesis route endowed kinetic stabilisation. • Non-preference of La3+ for 7-fold capped octahedra yields wide orthorhombic field. • Extremely low field independent leakage current (4 × 10−5 μA/mm2) observed for GdInO 3. • New lead-free relaxor by A-site distortion by 40 mol%La3+ substitution in h-GdInO 3. [ABSTRACT FROM AUTHOR]