V4+ ESR, dielectric properties and superionic conductivity in monocrystalline NaTiOPO4

A method of obtaining NaTiOPO4 monocrystals alloyed by vanadium was described. V4+ ESR in NaTiOPO4 in 3 cm range of wavelengths at T = 300-870 K was studied. Constants of spin-hamiltonian (T = 300 K) were determined, as well as directions of magnetic axes of paramagnetic centres. The angles between magnetic axes z of paramagnetic centres and crystallographic direction [100], [010], and [001] are 19, 71, 124 deg for the type I centres; 19, 109, 124 deg - for the type 2 centres. A model of the paramagnetic centres is suggested. Temperature dependences of dielectric permittivity ε, dielectric losses tg δ and conductivity δ in the range of 4.2-870 K were measured. At the temperatures above 400 K growth of ε, tg δ and δ close to the exponential one was detected along different crystallographic directions with distinctly pronounced anisotropy along a axis, where conductivity is the highest. At the temperatures above 520 K the presence of superionic conductivity is assumed. 15 refs.; 4 figs