Growth and optical properties of transition metal oxides single crystal solid solutions
Abstract NiO, CoO, MnO single crystals and single crystal solid solutions of Ni c Mg 1− c O, Co c Mg 1− c O and Mn c Mg 1− c O were grown by the method of chemical transport reaction (the “sandwich” technique). The nature of the observed absorption and luminescence bands is explained in terms of the electronic transition of bivalent nickel, cobalt and manganese. The fine structure of the observed bands in NiO and MnO are connected to the pure exciton transition and to the exciton-magnon excitation.
Origins and Control of Optical Absorption in a Nondilute Oxide Solid Solution: Sr(Ti,Fe)O3–x Perovskite Case Study
Understanding and rationally tailoring defect-mediated optical absorption of nondilute oxide solid solutions represents a complex challenge. In this work, we investigate compositions in the SrTiO3–SrFeO2.5 solid solution, departing from the simpler dilute Fe-substituted SrTiO3 case. Through ex situ and in situ optical absorption measurements of mixed conducting thin films prepared by pulsed laser deposition and through density functional theory simulations, we demonstrate understanding and rational tailoring of the optical absorption behavior. Experimentally, broad subgap absorption peaks, centered around 2.1 and 2.8–3 eV, increase in intensity with increasing Fe and/or O concentrations and decrease with increasing La donor dopant concentration. Consistent with these observations, the absorption is found to be proportional to the hole concentration and to the Fe concentration under fully oxidized conditions. This behavior is similar to the dilute case; however, the solid solution electronic structure and ...
DIFFERENTIAL CALCULUS OF SEVERAL VARIABLES WITH MATHEMATICA OR MAPLE
The use of Computer Algebra Systems (CAS) in Mathematical Laboratories at Engineering Schools is increasing. Therefore, it has become necessary to undertake a new educational approach in the teaching of many mathematical topics. Obviously it is not possible to give the same lectures as in the 1950,s. The CAS allows us to experiment and teach in “a different way”. The students' mathematical knowledge at the beginning of their studies in the University is completely different. Moreover we have fewer credits assigned to Mathematical topics in engineering curriculum. The objective of he authors, professors of different Spanish Universities, is to try to demonstrate a new way to use the CAS, concretely Maple and Mathematica, as a support in the teaching of Differential Calculus of Several Variables. They take advantage of the computer's graphical capacities to sketch the graphs of surfaces defined in explicit, parametric or implicit form. They survey the general topics: limits, partial derivatives, differentiability, chain rule, implicit functions and extreme values. For each topic, they give a few basic instructions of the CAS used; afterwards they give several examples, in increasing order of difficulty, and finally the students must solve exercises and try to establish a general procedure for a quite general problem. In this paper we have included several examples used in this survey.