Thermoelectric materials are competitive candidates for special cooling applications. Mg₃Sb₂-based materials consisting of inexpensive ingredients have profound thermoelectric properties. At present, alloying with Mg₃Bi₂ is the most effective approach to optimize the thermoelectric properties of Mg₃Sb₂-based materials. However, the extremely low abundance of bismuth in the crust contradicts its economic expectation. In this work, the ZrO₂ micro-particles were separated into the Mg_3.2Sb_1.99Te_0.01. The doping effect of Zr atoms at Mg sites increased the electrical conductivity, and the combined secondary phase lowered the lattice thermal conductivity. With acceptable degradation in the Seebeck coefficient, the sample combined with 5% (in mass) ZrO₂ exhibited a dimensionless figure of merit (zT) of 0.49 and a power factor of 2.7 mW·m⁻¹·K⁻² near room temperature. The average zT in the range from 300 K to 500 K reached 0.8, on par with the Mg₃Sb₂Mg₃Bi₂ alloys. Besides, the compressive and bending strengths reach 669 MPa and 269 MPa, respectively, far superior to the common room-temperature thermoelectrics. This secondary phase showed a surprising and uncostly promotion of the Mg₃Sb₂-based thermoelectric materials, impelling the realization of its commercial application.

BiFeO₃–BaTiO₃ (BF–BT) based piezoelectric ceramics are a kind of high-temperature lead-free piezoelectric ceramics with great development prospects due to their high Curie temperature (T_C) and excellent electrical properties. However, large leakage current limits their performance improvement and practical applications. In this work, direct current (DC) test, alternating current (AC) impedance, and Hall tests were used to investigate conduction mechanisms of 0.75BiFeO₃–0.25BaTiO₃ ceramics over a wide temperature range. In the range of room temperature (RT)−150 ℃, ohmic conduction plays a predominant effect, and the main carriers are p-type holes with the activation energy (E_a) of 0.51 eV. When T > 200 ℃, the E_a value calculated from the AC impedance and Hall data is 1.03 eV with oxygen vacancies as a cause of high conductivity. The diffusion behavior of thermally activated oxygen vacancies is affected by crystal symmetry, oxygen vacancy concentration, and distribution, dominating internal conduction mechanism. Deciphering the conduction mechanisms over the three temperature ranges would pave the way for further improving the insulation and electrical properties of BiFeO₃–BaTiO₃ ceramics.

The field of artificial intelligence and neural computing has been rapidly expanding due to the implementation of resistive random-access memory (RRAM) based artificial synaptic. However, the low flexibility of conventional RRAM materials hinders their ability to mimic synaptic behavior accurately. To overcome such limitation, organic-2D composites with high mechanical properties are proposed as the active layer of RRAM. Moreover, we enhance the reliability of the device by ZrO₂ insertion layer, resulting in stable synaptic performance. The Ag/PVA:h-BN/ZrO₂/ITO devices show stable bipolar resistive switching behavior with an ON/OFF ratio of over 5 × 10², a ~2400 cycles endurance and a long retention time (>6 × 10³s), which are essential for the development of high-performance RRAMs. We also study the possible synaptic mechanism and dynamic plasticity of the memory device, observing the transition from short-term potentiation (STP) to long-term potentiation (LTP) under the effect of continuous voltage pulses. Moreover, the device exhibits both long-term depression (LTD) and paired-pulse facilitation (PPF) properties, which have significant implications for the design of organic-2D composite material RRAMs that aim to mimic biological synapses, representing promising avenues for the development of advanced neuromorphic computing systems.

BiFeO₃-BaTiO₃ based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature. Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering, in this work, the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy (PFM) and switching spectroscopy piezoresponse force microscopy (SS-PFM), which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale. The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature. The maximum piezoresponse (R_s), remnant piezoresponse (R_rem), maximum displacement (D_max) and negative displacement (D_neg) at 45 V and 120 ℃ reach 122, 69, 127 pm and 75 pm, respectively. Due to the distinct effect of poling engineering in full domain switching, the corresponding d₃₃ at 50 kV/cm and 120 ℃ reaches a maximum of 205 pC/N, which is nearly twice as high as that at room temperature. Studying the evolution of ferroelectric domains in the poling engineering of BiFeO₃-BaTiO₃ ceramics provides an insight into the relationship between domain structure and piezoelectric response, which has implications for other piezoelectric ceramics as well.