In situ Profiles of Oxygen Diffusion in SrTiO₃: Bulk Behavior and Boundary Effects

Abstract

Oxygen content and oxide kinetics determine response time Diffusion profiles have been recorded in situ and evaluated in bulk conductivity sensors, drift effects in surface conductivusing an optical technique. In this way, bulk diffusion coefity sensors, speed of oxygen permeation in chemical filters, ficients have been reliably and quantitatively measured. It performance of oxide electrodes, lifetime in some perovskite is shown that the values agree with calculations without capacitor materials stressed by applied voltage, annealing temusing adjustable parameters if the coupling of the diffusperature in high-temperature superconductors, 11,13 and other ing species to internal redox changes of the dopants is phenomena. accounted for. Measurements on single crystals and on bicrystals with and without crack formation provide worthwhile information on the influence of free relaxed surfaces, II. Experimental Procedure freshly produced (crack) surfaces, and grain boundaries onMeasurements were performed on single crystals and bicrysthe surface reaction rate and diffusional process.

How Is Oxygen Incorporated into Oxides? A Comprehensive Kinetic Study of a Simple Solid‐State Reaction with SrTiO3 as a Model Material

“…Such profiles can be recorded in an elegant way on single-crystal or bicrystal samples by in situ spatially resolved optical spectroscopy. [37] Characteristic examples are shown in Figure 5. If the surface reaction is slow relative to the chemical bulk diffusion (the borderline is represented by…”

“…In Stuttgart, we developed an optical method that allows us to follow in situ the oxygen incorporation kinetics into strontium titanate as a function of space and time, and much of the progress to be reported is due to this development. [22,37] The detailed reaction steps can be roughly classified as 1) surface reaction including chemical kinetics at the surface and transport through the subsurface layer, 2) bulk transport, 3) transport across (or along) internal boundaries (the transport along grain boundaries has not yet proven to be important for SrTiO 3 ; nevertheless, we give general information in particular in terms of treating polycrystalline matter). This classification also determines the structure of this Review.…”

“…Recently, substantial progress was achieved in several respects, for example: 1) in the understanding of elementary chemical reaction steps at gassolid interfaces; [8][9][10][11][12] 2) in connecting elementary rate constants with effective parameters measured in relaxation kinetics; [13][14][15][16][17] 3) in including space charges into chemical diffusion; [18][19][20] 4) in taking into account coupling diffusion with internal reactions; [21,22] 5) in the study of complex and nonlinear processes. [23][24][25][26][27][28][29][30][31][32][33] On the experimental front, the development of specific in situ techniques has contributed to the in-depth understanding of defect chemistry and transport (see, for example, references [23,[34][35][36][37]). …”

Anomalously large measured thermoelectric power factor in Sr1−xLaxTiO3 thin films due to SrTiO3 substrate reduction

“…Normally, an SrTiO 3 (001) single-crystal substrate subjected to the thermodynamic conditions of our thin-film growth for samples presented in this paper (p O2 = 10 -7 Torr, 450°C, 10-60 minutes) will not become appreciably reduced nor conductive 20 ; nevertheless only light doping of the substrate is required to give it a relatively small total resistance. The 500 µm-thick substrate (2.5x10 3 times the volume of the thin-films) requires a resistivity only 10 -3 times that of the film's resistivity to become a significant factor in any transport measurement assuming a uniform distribution of oxygen vacancies, and it must also be considered that short-circuit conductive paths with even lower resistivity may form along dislocations 21 close to the value reported 9,11 for that of two-dimensional thermoelectrics on STO substrates.…”

Wie wird Sauerstoff in Oxide eingebaut? Kinetische Studie einer “simplen” Feststoffreaktion am Modellmaterial SrTiO3

“…[23][24][25][26][27][28][29][30][31][32][33] Auf experimenteller Seite hat die Entwicklung spezifischer In-situ-Methoden zu einem tiefgehenden Verständnis von Defektchemie und Transport beigetragen (siehe etwa Lit. [23,[34][35][36][37]). …”