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.