EPR and optical absorption studies of Cu2+ and VO2+ impurities in diammonium d-tartarate single crystal grown in ammonium dihydrogen phosphate buffer

The study is extended by growing the Cu2+ and VO2+ doped diammmonium d-tartarate single crystal in buffered solution with different pH values and the results are discussed referring to the color center forming property by means of transition metal impurities which are stable point defects. XRD study shows that the crystals grown in ammonium dihydrogen phosphate buffer with pH value of 5.9 which is smaller than that of water, the monoclinic symmetry of the crystal changes to orthorhombic and the number of paramagnetic centers is doubled. The spin-Hamiltonian parameters are determined and the ground state wave functions of Cu2+ ions are constructed. The optical absorption spectrum of both Cu2+ and VO2+ doped single crystals show three absorption bands corresponding to the splitting of d orbitals of metal ions in octahedral environment with tetragonal distorsion. Two of the bands lie in visible range and third one lies in infrared region.