The stabilization mechanism of antiferroelectric (AFE) phases in sodium niobate (NaNbO₃, NN) ceramics remains unclear, leading to irreversible AFE–ferroelectric (FE) phase transitions and the need for a high operating electric field (E-field), which significantly limits the utilization of AFE properties. In this work, leveraging insights from density functional theory calculations, we design and fabricate xBi_2/3SnO₃–(1−x)NaNbO₃ ceramics, overcoming these limitations by achieving both a reversible AFE–FE phase transition and a low operating field (< 200 kV/cm). Notably, the optimized composition results in exceptionally low remanent polarization compared with that of conventional AFE systems. Structural analysis reveals a three-stage phase evolution with increasing x: FE Q phase (Pmc2₁, Glazer tilt system: a⁻a⁻b⁺) + AFE P phase (Pbcm, Glazer tilt system: a⁻a⁻b⁺/a⁻a⁻b⁻) (x < 0.02) → pure AFE P phase (x = 0.02) → coexistence of AFE P phase + AFE R phase (0.02 < x < 0.08). The AFE P phase is characterized by a periodically arranged 4-layer multicell structure (~1.65 nm) that is disrupted by 6-layer antiphase boundaries (APBs, ~2.44 nm), which are associated with the dislocation formation and a large energy difference between the P and Q phases (7.20 meV/(f.u.)). These features likely contribute to a reduced domain size and a lower field-induced AFE → FE transition. Furthermore, the stabilization of the AFE R phase is caused primarily by a reduction in the distortion index (from 0.047 to 0.003) and enhanced covalency in A–O and B–O bonds. This study provides new insights and theoretical guidance for the development of low-field-driven reversible phase transitions in AFEs.

Power consumption is the energy source of the impact on fibers or pulp during low-consistency (LC) pulp refining, and the strength of refining affects refining quality and efficiency. The pulp properties, operating parameters, and bar parameters of the refiner plates are important parameters affecting refining efficiency, which can be defined as the ratio of net to total refining power. In this study, LC refining trials for pulps with different consistencies and fiber lengths were conducted using five isometric straight-bar plates with different bar angles to explore the influences of the plate bar angle and pulp properties on the no-load power, impact capacity on fibers and refining efficiency. It was found that the no-load power of the LC refining process decreased with an increase in the plate bar angle while increased when pulp with higher consistency was refined under the same refining conditions. However, the effect of pulp consistency on the no-load power can be neglected when refining is conducted using plates with larger bar angles. Meanwhile, a critical bar angle for straight-bar plates in LC refining may exist, which has the strongest impact on the pulp and highest refining efficiency under the same refining conditions. In addition, the impact capacity of the plate on the pulp and refining efficiency in LC refining can be enhanced by appropriately increasing the pulp consistency and average fiber length when the bar angle of the refiner plate with a sector angle of 40° is less than 30°. Therefore, the efficiency and power consumption of the LC refining process can be adjusted by optimizing the pulp consistency and bar parameters of the refining plates.