Enhanced photostriction in high-entropy ilmenite-type ceramics under visible light
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Sample preparation CNMMC, CNMM and CNM were synthesised via a solid-state reaction using high-purity Co3O4 (99.0%), Ni2O3 (99.0%), MnO2 (99.0%), MgTiO3 (99.0%), CuO (99.0%) and TiO2 (99.0%), which were obtained from Macklin Biochemical Co., Ltd. (Shanghai, China). The raw materials were stoichiometrically weighed and ball-milled using zirconia balls in ethanol for 10 h. The resulting mixtures were dried and calcined at 1100 °C for 5 h. The obtained precursors were further ball-milled for 10 h and dried, yielding high-entropy ilmenite-type powders. These powders were sintered under 30 MPa at 1000 °C–1100 °C for 5 min using a spark plasma sintering system (AC-FPS-5T; Ningbo Chenxin Weike Industrial Technology Co., Ltd., Ningbo, China). Finally, the as-prepared samples were cut into specimens with dimensions of 2 mm × 7 mm × 1 mm using a low-speed diamond saw (SYJ-150; MTI Corporation, Richmond, CA, USA) for thermal expansion measurements and thinned to dimensions of 2 mm × 7 mm × 0.2 mm for photostriction measurements. Physical characterisation The phase structures of CNMMC, CNMM and CNM were examined via XRD using a Cu Kα source with a 2θ precision of 0.0001° (D8 ADVANCE; Bruker, Karlsruhe, Germany). Their microstructures were observed using SEM (S4800; Hitachi, Tokyo, Japan), energy dispersive spectroscopy (EDS, EMAX, HORIBA Ltd., Kyoto, Japan), TEM (Tecnai G2 F30; FEI Ltd., Hillsboro, OR, USA) and aberration-corrected transmission electron microscopy (AC-TEM) (JEM ARM 200F, JEOL Ltd., Tokyo, Japan). The chemical states and chemical environment of the metal elements were analyzed by X-ray photoelectron spectra (XPS, Nexsa G2, Thermo Fisher Scientific, Waltham, Massachusetts, USA) with Al Kα X-ray source and pass energy of 50 eV. All XPS spectra were calibrated to the C1s peak at 284.8 eV. Electron paramagnetic resonance spectra (EPR, A300-10/12, Bruker, Germany) were recorded at 77 K under liquid nitrogen cryogenic environment. Their UV–Vis absorption spectra were recorded using the diffuse reflection method with a UV–Vis–NIR spectrophotometer (UV-3600; Shimadzu, Kyoto, Japan), and an integrating sphere covered with BaSO4 was utilised as the reference. Their thermal expansion coefficients were measured using a dilatometer (DIL 801; TA Instruments, Newcastle, DE, USA) at a heating rate of 2 °C/min. Their Raman spectra were recorded using a laser Raman spectrometer (inVia; Renishaw, Wotton-under-Edge, UK) with 532 nm and 785 nm laser excitation. Photostriction measurements Photostriction measurements were performed on CNMMC, CNMM and CNM using a dilatometer (DIL 801, TA Instruments). Sample temperature was monitored using the built-in thermocouple thermometer. Three laser sources with different wavelengths (405, 520 and 650 nm) were employed for irradiation: HSGD16-405AD200, HSGD16-520AD150 and HSGD16-650AD200 (HSG Laser Co., Ltd., Guangdong, China).
Institutions
- Henan University of EngineeringHenan, Zhengzhou