Electron paramagnetic resonance and electron–nuclear double-resonance study of Ti³ centres in KTiOPO₄

Abstract

Electron paramagnetic resonance and electron–nuclear double resonance have been used to characterize four Ti3+ centres in undoped crystals of potassium titanyl phosphate (KTiOPO4 or KTP). These 3d1 defects (S = 1/2) are produced by ionizing radiation (either 60 kV x-rays or 355 nm photons from a tripled Nd:YAG laser), and form when the regular Ti4+ ions in the crystal trap an electron. Two of these trapped-electron centres are only observed in hydrothermally grown KTP and the other two are dominant in flux-grown KTP. Both of the Ti3+ centres in hydrothermally grown crystals have a neighbouring proton (i.e. an OH− molecule). In the flux-grown crystals, one of the Ti3+ centres is adjacent to an oxygen vacancy and the other centre is tentatively attributed to a self-trapped electron (i.e. a Ti3+ centre with no stabilizing entity nearby). The g matrix and phosphorus hyperfine matrices are determined for all four Ti3+ centres, and the proton hyperfine matrix is determined for the two centres associated with OH− ions. These Ti3+ centres contribute to the formation of the grey tracks often observed in KTP crystals used to generate the second harmonic of high-power, near-infrared lasers.

Flight to Mars and radiation defects in Li2B4O7 and KTiOPO4 crystals

“…Some of observed EPR lines have spin-Hamiltonian characteristics, which are close to the parameters described Cr 3+ and Fe 3+ [1][2][3]. However, many lines do not belong to paramagnetic centers, which were identified previously [4][5][6][7][8][9][10]. Intensities of additional EPR lines, which appeared after γ-irradiation, correlated with the concentrations of non-controlled impurities.…”

Theoretical research of the spin-Hamiltonian parameters for two rhombic W5+ centers in KTiOPO4 (KTP) crystal through a two-mechanism model

“…The crystals properties can be modified by the impurities, e. g., transition-metal and rareearth ions, thus affecting the applications. Hence, the spectroscopic studies of KTP crystals doped by impurities, which can provide information on the impurity energy levels, the defect models and structures in the doped crystals, have received significant attention [10][11][12][13][14][15][16][17]. Bravo et al, [17] measured the EPR spectra of W-doped KTP crystal and found two approximately rhombic W 5 þ centers, which belong to the first-kind rhombic center defined in Ref.…”

Hyperfine structure associated with the dominant radiation‐induced trapped hole center in RbTiOPO4 crystals

“…The g matrix and the hyperfine matrices obtained from the resulting electron paramagnetic resonance (EPR) and electronnuclear double resonance (ENDOR) spectra then verify the existence of an alkali vacancy next to the unpaired spin. Trapped holes located next to potassium vacancies have been observed in KTP crystals [15][16][17], and Laruhin et al [18] have suggested that similar hole centers associated with rubidium vacancies are produced in RTP crystals.…”