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BaTiO3 hollow nanofibers were fabricated by electrospinning and then subsequent calcination of as-spun nanofibers with a heating rate of 2.5 °C/min. Scanning electron microscope and transmission electron microscope (TEM) results indicated that the heating rate had a significant effect on the morphology of the BaTiO3 hollow nanofibers. The X-ray diffraction, Raman spectroscopy, and TEM results indicate the prepared BaTiO3 hollow nanofibers have tetragonal phases. From the results of the X-ray photoelectron spectroscopy analysis, in the amorphous BaTiO3 nanofiber, peaks at 457.2 eV for Ti 2p3/2 were also found, which corresponded to the Ti3+ ions. However, in the crystalline BaTiO3 nanofibers, peaks of Ti 2p3/2 showed the Ti4+ ions. Intense visible photoluminescence was observed in the amorphous BaTiO3 nanofiber, which is calcined below a temperature of 500 °C. The observed intense photoluminescence was ascribed to a multiphonon process with localized states within the band gap of the highly disordered states. In the crystalline BaTiO3 hollow fiber, low intensity of photoluminescence showed at the visible region, which is originated from an intrinsic Ba defect.

Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 (0≤x≤1) thin films prepared by metal organic decomposition process were fabricated on SiN/Si substrate for infrared sensor application. Their structural and electrical properties were investigated with variation of Cu dopant. The [(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 (CCNMO) film annealed at 500℃ exhibited a dense microstructure and a homogeneous crystal structure with a cubic spinel phase. Their crystallinity was further enhanced with increasing doped Cu amount. The 120 nm-thick CCNMO (x=0.6) thin film had a low resistivity of 53 Ω•cm at room temperature while the Co-free film (x=1) showed a significantly decreased resistivity of 5.9 Ω•cm. Furthermore, the negative temperature coefficient of resistance (NTCR) characteristics were lower than -2%/℃ for all the specimens with x≥0.6. These results imply that the CCNMO (x≥0.6) thin films are a good candidate material for infrared sensor application.

Copper manganite thin films were fabricated on SiNx/Si substrate by metal organic decomposition (MOD) process. They were burned-out at 400℃ and annealed at various temperatures (400 ∼800℃) for 1h in ambient atmosphere. Their micro-structure and negative temperature coefficient of resistance (NTCR) characteristics were analyzed for micro-bolometer application. The copper manganite film with a cubic spinel structure was well developed at 500℃ which confirmed by XRD and HRTEM analysis. It showed a low resistivity (47.5 Ω•cm) at room temperature and high NTCR characteristics of -4.12%/℃ and -2.15%/℃ at room temperature and 85℃, implying a good thin film for micro-bolometer application. Furthermore, its crystallinity was enhanced with increasing temperature to 600℃. However, the appearance of secondary phase at temperatures higher than 600℃ lead to deteriorate the NTCR characteristics.