Simultaneous enhancement of recoverable energy density and efficiency of lead-free relaxor-ferroelectric BNT-based ceramics.

• Ruddlesden-Popper type polycrystals La 3 Ni 2 O 7 /LaNiO 3 and La 2 NiO 4 /La 2 O 3 were synthesized. • The structural and electromagnetic properties were analyzed. • The interstitial O2– and V O in polycrystals were studied based on XPS and XRD. • The RL of La 3 Ni 2 O 7 /LaNiO 3 and La 2 NiO 4 /La 2 O 3 reached –22.63 and −50.06 dB in S-band. Given the remarkable performances of Ruddlesden-Popper (RP) type oxides in electronic devices, the study of their intrinsic dielectric, magnetic and electromagnetic microwave (EMW) absorption properties are still missing. Herein, two kinds of Lead-free relaxor-ferroelectric BNT-based ceramic hierarchical polycrystalline alloys (La 3 Ni 2 O 7 /LaNiO 3 , La 2 NiO 4 /La 2 O 3) were prepared via a facile solvothermal and high-temperature annealing technique as high-performance EMW absorption materials (MAMs). By a means of adjustment of solvothermal time in the precursor systems, Nickel salt layers precipitation declined gradually. The phase and crystal state of the powders were characterized by X-ray diffraction (XRD) with refinement treatment (Rietveld analysis). XPS was utilized on the determination of interstitial O2– quantitatively in La 3 Ni 2 O 7+δ (δ = 1.95) and La 2 NiO 4+δ (δ = 0.75). Responsible to the synergistic effect of dielectric and magnetic response and well-matched impedance, the as-fabricated MAMs performed excellent wave absorbability, especially in low frequency (S-band). In details, La 3 Ni 2 O 7 /LaNiO 3 achieved optimal effective absorption band (f E) 3.36 GHz at 9.52–12.80 GHz and a minimum reflection loss (RL min) −43.30 dB with a thickness of 2.2 mm. Moreover, La 3 Ni 2 O 7 /LaNiO 3 and La 2 NiO 4 /La 2 O 3 overcame the challenge of absorbers' thickness in S-band, of which the RL reached –22.63 and −29.90 dB at 0.7 mm, respectively. Noteworthily, La 3 Ni 2 O 7 /LaNiO 3 obtained RL value of −50.06 dB at 10.72 GHz with a device thickness of 2.8 mm. It is emphasized that this report has interpreted the EMW absorption capacity and mechanism exhaustively, which will initiate simultaneous enhancement of recoverable energy density and efficiency application of RPs. [ABSTRACT FROM AUTHOR]