ABSTRACT
Spinel structured highly dense NiMn2O4-based (NMO) negative temperature coefficient (NTC) thermistor thick films were fabricated by aerosol-deposition at room temperature. To enhance the thermistor B constant, which represents the temperature sensitivity of the NMO thermistor material, Co and Co-Fe doping was applied. In the case of single element doping of Co, 5 mol% doped NMO showed a high B constant of over 5000 K, while undoped NMO showed -4000 K. By doping Fe to the 5 mol% Co doped NMO, the B constant was more enhanced at over 5600 K. The aging effect on the NTC characteristics of Co doped and Fe-Co co-doped NMO thick film showed very stable resistivity-time characteristics because of the highly dense microstructure.
Subject(s)
Aerosols/chemistry , Cobalt/chemistry , Iron/chemistry , Membranes, Artificial , Metal Nanoparticles/chemistry , Metal Nanoparticles/ultrastructure , Hot Temperature , Materials Testing , Molecular Conformation , Particle Size , Surface Properties , Thermal ConductivityABSTRACT
A reversibly mechanochromic conjugated polymer has been developed. The polymer, polydiacetylene (PDA), obtained by thermal polymerization of a diphenyldisulfide-containing bisdiacetylene undergoes a blue-to-green color change upon grinding. The original blue color of the PDA is regenerated via a metastable red-color state by utilizing a thermochromic (heating-cooling) process.
ABSTRACT
Thick polycrystalline pure PbTiO3 films with nano size grains were synthesized for the first time by aerosol deposition. Annealed 7 µm thick films exhibit well-saturated ferroelectric hysteresis loops with a remanent polarization and coercive field of 35 µC/cm(2) and 94 kV/cm, respectively. A large-signal effective d33,eff value of >60 pm/V is achieved at room temperature. The measured ferroelectric transition temperature (Tc) of the films â¼550 °C is >50 °C higher than the reported values (â¼490 °C) for PbTiO3 ceramics. First-principles calculations combined with electron energy loss spectroscopy (EELS) and structural analysis indicate that the film is composed of nano size grains with slightly decreased tetragonality. There is no severe off-stoichiometry, but a high compressive in-plane residual stress was observed in the film along with a high transition temperature and piezoelectric response. The ferroelectric characteristics were sustained until 200 °C, providing significant advancement toward realizing high temperature piezoelectric materials.