Polarization Dependence of the Cr³⁺ R‐Line Fluorescence from Sapphire and Its Application to Crystal Orientation and Piezospectroscopic Measurement

Abstract

unless microfocus facilities are available. One motivation of The room-temperature polarization characteristics of the the present study is to develop a technique to determine the ruby R lines have been studied by monitoring the fluorescrystallographic orientation of small regions of Al 2 O 3 by studycence intensity as a function of excitation direction relative ing the polarization characteristics of their R-line fluorescence. to the crystallographic axes of the ruby crystal. The R linesAdditionally, precise knowledge of the fluorescence polarizaare strongly polarized in the basal plane but have no pretion is important in stress measurements in polycrystalline ferred vibration direction within the basal plane. However, materials, in which the stress-induced line shifts are averaged the degree of polarization, P, of the R1 and R2 lines is not over all possible crystallographic orientations and a weighting the same, being P R1 ‫؍‬ 87% and P R2 ‫؍‬ 62%. The phenomefunction resulting from the polarization dependence may need non is explained in terms of the absorption anisotropy and to be included. the probability of spontaneous emission. The findings pro-The anisotropic absorption properties have been commonly vide the basis for a high-spatial-resolution spectrophotoused to align optically uniaxial crystals with their optical axes, metric method to determine the optical c-axis of chromiumat least qualitatively. Although the emission process is more doped Al 2 O 3 crystals using the angular dependence of the complex than that of the absorption, the ruby fluorescence intensity ratio of the R2 line to the R1 line. The application should inherit the optically uniaxial properties from the corunto the orientation determination of sapphire fibers embeddum structure. In this work, a series of experiments were perded in composites and the corresponding residual stress formed to study the polarization characteristics of R-line components are discussed together with the possibility of fluorescence. As a result, the intensity ratio (R2/R1) is determeasuring the texture in the Al 2 O 3 polycrystalline thin films mined as a function of the angle between the optical c-axis of such as oxidation scales. Furthermore, the consequences of the crystal and the direction of the E vector of the incident light polarization orientation on piezospectroscopic measureso that it can be used to measure the c-axis orientation in Al 2 O 3 ments are discussed.quantitatively. After a brief description of the experimental procedures, the results obtained are presented in Section III. I. IntroductionThe theoretical interpretation described in Section IV, along with a comparison with previous literature data, is then fol-T HE optical spectra of ruby (Cr 3ϩ -doped sapphire) have been lowed by examples of application of this phenomenon. studied extensively since the late 1950s and are generally considered to be well interpreted in terms of ligand field theory. 1-5 As a result, the polarization of ruby absorption is well under-II. Experimental Details sto...

Microstructure and mechanical properties of Al2O3–YSZ and Al2O3–YAG directionally solidified eutectic plates

“…This behaviour can be used to calculate the residual stresses in the alumina phase from the values of the piezospectroscopic tensors, ij , as determined by He and Clarke. 19 They are diagonal with respect to the ruby crystallographic axes. Assuming that the piezo-spectroscopic effect is isotropic in the alumina basal plane, 11 ≈ 22 , the peak shift ν between the stressed and unstressed ruby is given for the two R 1 and R 2 lines by: where σ ii (i = 1, 2, 3) stand for stress components along the a-, m-and c-axes of the hexagonal sapphire lattice, respectively.…”

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

“…At least part of the motivation for the polycrystalline research was to investigate the stress fields arising in polycrystalline alumina responsible for microcracking-the spontaneous localized cracking that occurs in polycrystalline alumina on cooling as a consequence of the anisotropic structure and thermal expansion of corundum [39][40][41]. From the 1990s onward, although there were many notable fundamental studies of the phenomenon [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58], the shift in energy of R lines with stress was largely confined to the applied domain, detailed in numerous works, such as: measurement of stress in bulk Al2O3 polycrystals [42,[58][59][60][61][62][63][64][65][66][67]; in bulk Al2O3-ZrO2 composites [68][69][70][71][72][73][74][75][76][77][78]; in sapphire or composite fibers, free or in matrices [79][80]…”

The Influence of La Doping on the Oxidation Mechanism and Stresses in the Thermally Grown Oxide on CMSX-4 with Pt-Aluminide Bond Coat

“…The peak height ratio of the R1 and R2 luminescence peaks (H R1 /H R2 ) can be used to determine whether there is preferential orientation in the polycrystalline a-Al 2 O 3 . The R lines are strongly polarized in the basal plane but have no preferred vibration direction within the basal plane [24]. Thus the peak intensity ratio is dependent on the orientation of the crystal [24].…”

“…The R lines are strongly polarized in the basal plane but have no preferred vibration direction within the basal plane [24]. Thus the peak intensity ratio is dependent on the orientation of the crystal [24]. Using a single crystal sapphire and a 59 objective lens, the peak height ratio (H R1 /H R2 ) was determined as 1.88 when the basal plane of the single crystal sapphire was placed facing (in normal to) the laser incidence direction (optical axis of the system).…”