The effect of pressure on luminescence properties of Cr 3+ ions in LiSc(WO 4) 2 crystals—Part I: Pressure dependent emission lineshape

Abstract

We report the results of high-pressure studies of spectral properties in Cr 3+-doped LiSc(WO 4) 2 crystals between ambient pressure and 260 kbar. The effect of pressure on the present system has led to a structural transformation for pressure 60–88 kbar and a low-field → high-field spectral transformation of the Cr 3+ emission for pressure 117–227 kbar. The pressure-induced spectral transformation provided the opportunity to distinguish two distinct Cr 3+ sites in the host lattice. We have attributed them to the Cr 3+ ions that occupy the Li + and Sc 3+ sites. For both sites we observed that energy of the 2E excited state of Cr 3+ was lower than 14,000 cm −1 and exhibited pressure-induced red shift of about −2.5 cm −1/kbar. We have also observed the large inhomogeneous broadening of the 4T 2→ 4A 2 and 2E→ 4A 2 emissions. We have completed a quantitative analysis of the relative emission intensities of the 2E→ 4A 2 and 4T 2→ 4A 2 transitions as a function of pressure and temperature to study the distribution of the crystal field and electron–phonon coupling of the Cr 3+ in the host lattice. As the result we have recovered a functions that describe the distribution of the energy of 4T 2 state and electron–lattice coupling ( S - 1 2 ) ℏ ω in considered material.