Terahertz response of Er3+/Yb3+ co-doped La2Zr2O7 synthesized using the sol-gel precipitation method

Oxide ceramics with pyrochlore structure such as La 2 Zr 2 O 7 are promising materials for advanced multifunctional applications including extreme environment, such as space applications. They combine low thermal conductivity, suitable coefficient of thermal expansion to join supporting materials and have optical response in the UV–VIS region with up-converting and down-converting properties after doping, required for coating, sensors, and electro-optic applications. The effect of doping elements such as Er 3+ and Yb 3+ , replacing isomorphically lanthanum in the La 2 Zr 2 O 7 with pyrochlore cubic structure, on material photophysical properties was investigated by selective doping, in the molar ratio of Er 3+ /Yb 3+ ranging from 0.5 to 5. The reflectance spectra of materials prepared by sol-gel co-precipitation method after sintering at 1400 °C, investigated in the UV–VIS–NIR range showed as expected well resolved absorptions due to the 4f–4f intra-configurational transitions. At the same time, dielectric properties of sintered samples were investigated by terahertz time domain spectroscopy. The refractive indices observed in the range of ~4.46–5.15, indicate high dielectric permittivity at THz frequencies applicable in energy storage materials or THz communication components. For all samples a broad absorption band was found in the THz region and the band intensities were clearly associated with the doping amount of Er and Yb cations into the La 2 Zr 2 O 7 structure, at frequencies 0.75–1.02 THz. Significant correlation at the level of R 2 = 0.911 was found between the absorption band corresponding to the 4 I 15/2 → 2 H 11/2 transition at 520.5 nm and the integrated intensities of THz bands. Dielectric ceramic materials such as titanium-, tantalum- and niobium- oxide based ceramics have permittivity in the range 20–30. The permittivity of studied La 2 Zr 2 O 7 was ~20 and increased after doping by Er 3+ /Yb 3+ to ~21–26. Intensity increase of absorption band in THz region after La 2 Zr 2 O 7 ceramic doping with Er and Yb. • La 2 Zr 2 O 7 doped with Er 3+ /Yb 3+ ratio ranging from 0.5 to 5 was synthesized. • Sintering at 1400 °C revealed cubic pyrochlore structure with luminescence properties. • Refractive indices of La 2 Zr 2 O 7 materials in the THz region were found to be 4.46–5.15. • A broad absorption band was found in pure and doped La 2 Zr 2 O 7 at 1.02–0.75 THz. • The integrated intensities of absorption band increased systematically with increasing Er/Yb ratio rising from 10 to 39 cm −1 THz.