Investigation of the optoelectronic properties of columbite ZnNb2O6 crystal

•The ZnNb2O6 crystals were grown by optical floating zone method.•The optical interband transitions of ZnNb2O6 were determined.•The useful optical constants for ZnNb2O6 crystal were obtained.

A high-quality ZnNb2O6 single-crystal grown by optical floating zone method has been used as a research prototype to analyze the optoelectronic parameters by measuring the absorption coefficient and transmittance spectra along the b-axis from 200 nm to 1000 nm at room temperature. The optical interband transitions of ZnNb2O6 have been determined as a direct transition with a band gap of 3.84 eV. The refractive index, extinction coefficient, and real and imaginary parts of the complex dielectric constants as functions of the wavelength for ZnNb2O6 crystal are obtained from the measured absorption coefficients and transmittance spectra. In the Urbach tail of 3.16–3.60 eV, the validity of the Cauchy–Sellmeier equation has also been evaluated. Using the single effective oscillator model, the oscillator energy Eo is found to be 4.77 eV. The dispersion energy Ed is 26.88 eV and ZnNb2O6 crystal takes an ionic value.