ESCA Studies of Yttrium Orthoaluminum Perovskites

Abstract

Room temperature X-ray photoelectron spectroscopy (XPS or ESCA) has been employed to investigate pure single crystals of yttrium aluminum perovskite (YAlO 3 (YAP)) and YAlO 3 doped with several rare earth elements, Y 1-x Ln x AlO 3 (Ln ) Pr, Er, Ho). XPS peak shapes of the main elements forming the YAP structure, in structures that have been doped with ions of varying oxidation states, are rationalized as a function of structural environment and the oxidation state of doping ions. The significant changes in chemical shifts and full widths at half-maximum of the signals are caused by doping and the presence of color centers. The most distinctive change in chemical shifts is observed for the O(1s) peaks. Annealing in H 2 /N 2 atmosphere (1200 °C) changes the color of the sample, removing color centers due to relocation of oxygen ions in the structure. Although the total amount of oxygen in the samples does not change, the relative ratio of oxygen ions occupying two independent positions in the structure changes on annealing. Only in the case of YAlO 3 without color centers is the composition of crystal close to the stoichiometric one. Also the Y(3d) and Al(2p) signals are shifted to higher binding energies for doped YAP crystals.

XPS characterization of YAlO3:Co single crystals

“…The aluminium content exhibits some deficiency while the oxygen content shows an excess in relation to the nominal value. As in earlier measurements, lower content of aluminum ions and excess of yttrium ions for pure as-grown YAP crystals was found [6]. This may be explained by the presence of the YAlO 3 blocks separated by yttrium oxide layers.…”

“…In comparison with YAG, YAP single crystals can be grown faster, have a smaller core and more favorable distribution coefficient for rare-earth dopants. Recently, XPS measurements for YAlO 3 single crystals, pure and doped with several rare earth elements (Ln = Pr, Er, Ho), were carried out [6]. However, these measurements were done from surfaces, which were not freshly broken under UHV condition and the additional oxygen line, related to adsorbed oxygen, was visible.…”

Origin of Color Centers in the Perovskite Oxide CeAlO3

“…Generally, in YAlO 3 there maybe three point defects: cation vacancy (V Ce , V Al ), anion vacancy (V O ) and antisite defect (Y Al , Al Y ). The point defects in YAlO 3 are investigated in detail in some references . For example, Chen et al.…”

“…Pawlak et al. deduced that the color center in YAO 3 may be related with oxygen vacancies in crystal bulk and doping will promote the presence of color centers . Baryshevsky et al.…”

Structure and spectroscopic properties of (AA′)(BB′)O3mixed-perovskite crystals

“…This procedure was successfully applied in a number of previous similar studies. [15][16][17][18] Broad survey scans with a scan range from 0 to 1100 eV were run to identify all elements present in the samples, and then detailed scans (∼20 eV wide) were recorded and deconvoluted to establish precise elemental peak locations.…”