The inherent trade-off between achieving high density and forming effective grain boundary barriers in BaTiO₃ thermistors limits the simultaneous attainment of low room-temperature resistivity (R₂₅) and a high positive temperature coefficient of resistance (PTCR) jump, hindering the development of miniaturized PTCR devices. To overcome this limitation, we optimized the grain boundary properties of BaTiO₃ (BTO)-based PTCR ceramics via nano-BTO incorporation (with and without acceptor doping), thereby promoting oxygen vacancy recombination and acceptor state formation at the grain boundaries. This multifaceted strategy yielded ceramics exhibiting a synergistic combination of high density, fine grains (~2 μm), and exceptional PTCR performance, characterized by a low R₂₅ (≤ 50 Ω·cm) and a high PTCR jump (≥10⁵) in the abstract display incorrectely. These PTCR ceramics exhibit characteristic ferroelectric domain configurations, with both ordinary and coherent domains observed, and optimized grain boundary potential barriers. This enhanced performance is attributed to significantly improved oxygen diffusion at the grain boundaries. Specifically, this nanoparticle dopant strategy promotes oxygen vacancy recombination, the formation of adsorbed oxygen species, and the oxidation of Mn at the grain boundaries, collectively establishing multiple effective surface acceptor states. This work represents a significant advancement in PTCR ceramic fabrication.

Transparent electro-optic (EO) ceramics of La-doped 0.75Pb(Mg_1/3Nb_2/3)O₃–0.25PbTiO₃ (0.75PMN–0.25PT) were prepared successfully. High transparency of 69% in the near-infrared (IR) wavelength (1550 nm) was achieved at 2 mol% La doping, meanwhile it shows an extremely high quadratic EO coefficient of 45.4×10⁻¹⁶ m²·V⁻², which is indispensable for applications in EO devices. The distribution of a polar nanodomain structure of the samples experiences disorder–order–disorder evolution in a La doping range. It is found that a parallelly-stacked polar nanodomain structure with an easier and faster polarization switching in the 2 mol% La-doped sample suggests that an ordering distribution of polar nanoregions would be critical to inducing large EO effect, transparency, and piezoelectric response. A triple-cavity tunable optical filter (TOF) with a single transmission peak and a tuning voltage below 30 V in a tuning range of 190–197 THz was designed based on our ceramics. The work is believed to bridge the relationship among doping-engineering, EO properties, and polarization behavior, which would guide the further optimization of transparent EO ceramics.

The thin film of heat-sensitive materials has been widely concerned with the current trend of miniaturization and integration of sensors. In this work, Mn_1.56Co_0.96Ni_0.48O₄ (MCNO) thin films were prepared on SiO₂/Si substrates by sputtering with Mn–Co–Ni alloy target and then annealing in air at different temperatures (650–900 ℃). The X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis indicated that the main crystalline phase of MCNO thin films was spinel crystal structure; the surface of the thin films was very dense and uniform. The electrical properties of the thin films were studied in the temperature range of –5–50 ℃. The MCNO thin film with a low room temperature resistance R₂₅ of 71.1 kΩ and a high thermosensitive constant B value of 3305 K was obtained at 750 ℃. X-ray photoelectron spectroscopy (XPS) analysis showed that the concentration of Mn³⁺ and Mn⁴⁺ cations in MCNO thin films is the highest when annealing temperature is 750 ℃. The complex impedance analysis revealed internal conduction mechanism of the MCNO thin film and the resistance of the thin film was dominated by grain boundary resistance.