A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K 0.09MnO3 (LCKMO)/zinc oxide (ZnO) heterojunction bilayers grown on ITO substrate by pulsed laser deposition (PLD) at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/Al exhibits reproducible rectifying characteristics and light current under continuous laser irradiation of = 325 nm. We report here the influence of LCKMO/ZnO bilayers' thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency (PCE) is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.
Surface electronic structure of solid materials plays a critical role in heterogeneous catalysis. However,surface chemical composition of the perovskite oxides is usually dominated by segregated A-site cations and the amount of oxygen vacancies is relatively low, which seriously restricts their catalytic oxidation property. Here, we prepare perovskite La_xSr_(1-x)CoO_(3-δ)(x = 0.3, 0.5, 0.7) with different Sr doping amount and experiment results show that perovskite LSCO with higher content of surface Sr possesses more oxygen vacancies and better catalytic activity. On this basis, we develop a new experimental strategy to create more surface oxygen vacancies to promote their CO catalytic activity. In this method, we use high active hydrogen atoms(BH^(4-)) as reductant to realize surface in-situ chemical composite modification of La_xSr_(1-x)CoO_(3-δ)(x = 0.3, 0.5, 0.7), which causes their surface reconstruction(surface Sr enrichment).The regulation mainly focuses on the atomic layer level without damaging their bulk phase structure.Different from traditional high temperature annealing under reducing atmosphere, this method is high-efficiency, green and controllable. Furthermore, we study the surface reconstruction process and demonstrated that it is atomic layer engineering on the surface of La_xSr_(1-x)CoO_(3-δ)(x = 0.3, 0.5, 0.7) by X-ray photoelectron spectroscopy(XPS) and X-ray absorption fine structure(XAFS). Our experiment results also show that these samples treated by this method exhibit superior activity for CO oxidation compared with original samples.
Epitaxial growth of SmFeO3/SrRuO3 was achieved on SrTiO3 substrates by the pulsed laser deposition(PLD)method at 973 K under oxygen partial pressure of 12.5 Pa.No Fe2+leakage was detected in our SmFeO3 film.The remanent polarization and coercive electric field of the thin film with a higher degree of orientation along(110)were 1.97μC/cm2 and 0.89×104 V/cm at room temperature,respectively.This film showed enhanced canted antiferromagnetism spin ordering compared with its corresponding powder materials.
采用脉冲激光沉积法在单晶SrTiO3(STO)基底上制备了La0.62Ca0.29K0.09MnO3(LCKMO)薄膜,通过调控基底温度获得了平整致密的膜层.利用二维面探X射线衍射仪和高分辨透射电子显微镜对薄膜结构进行了表征.结果表明,薄膜呈高质量取向外延生长,对应关系为{001}LCKMO||{001}STO.对薄膜的磁热性能研究表明,5 T下最大磁熵变为3.45 J/(kg·K),相对制冷效率为379.5 J/kg,磁熵半峰宽为110 K.
以MnO2,Ca(OH)2和La(OH)3为反应原料,在惰性气氛、低温(500℃)熔融KOH体系中合成了具有菱形钙钛矿结构Ca,K共掺杂的La0.64Ca0.25K0.11MnO3纳米材料,并对Mn的价态及磁学性能等进行了讨论.X射线光电子能谱(XPS)分析结果表明,La0.64Ca0.25K0.11MnO3纳米材料中的Mn具有三重混合价态,其零场冷却低温磁化率曲线表现出顺磁-铁磁转变,居里温度(Tc)为280 K.
