Thermal expansion, mechanical and optical properties of gallium and aluminum substituted Zn2TiO4 spinels. (November 2017)

• Record Type: Journal Article
• Authors: Perfler, Lukas; Kahlenberg, Volker; Jakopic, Georg; Schaur, Andreas; Tribus, Martina; Schmidmair, Daniela; Kaindl, Reinhard
• Is Part Of: Materials research bulletin. Volume 95(2017)
• Page Start: 367
• Page End: 379
• Publication Date: 2017-11
• Subjects: oxides -- mechanical properties -- optical properties -- crystal structure -- thermal expansion -- microstructure -- Raman spectroscopy; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2017.08.012
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: Highlights: Synthesis of novel Zn1.75 Ti0.75 Ga0.5 O4, Zn1.5 GaTi0.5 O4, and Zn1.75 Ti0.75 Al0.5 O4 spinels. Substitution of Ga/Al within Zn2 TiO4 results in an increased hardness and elastic modulus. The materials exhibit both a high refractive index ( n > 2.0) and a high hardness ( H > 10 GPa). Zn1.75 Ti0.75 Ga0.5 O4 exhibits a lower thermal expansion compared to the Zn1.75 Ti0.75 Al0.5 O4 spinel. The crystal structure of the spinels was investigated by X-ray diffraction and Raman spectroscopy. Abstract: Polycrystalline samples of new Zn1.75 Ti0.75 Ga0.5 O4, Zn1.5 GaTi0.5 O4, and Zn1.75 Ti0.75 Al0.5 O4 spinel were prepared by solid-state reactions. Phase analysis and structural investigations were carried out by powder X-ray diffraction and Raman spectroscopy. In situ high-temperature powder X-ray diffraction experiments enabled the investigation of the thermal expansion of the spinel-type compounds. To determine the mechanical properties, nanoindentation experiments were performed with a Berkovich diamond indenter tip. Analyses of the load–displacement curves revealed a high hardness ranging from 10.2 ± 0.4 GPa to 11.8 ± 0.5 GPa and a reduced elastic modulus of 162 ± 5 GPa up to 178 ± 6 GPa. Furthermore, the optical properties of the spinel-type materials were studied by spectroscopic ellipsometry in the wavelength range of 250–1000 nm. All materials exhibit a high refractive index ranging from n = 2.20 to n = 2.10 at 430.8 nm (Fraunhofer G line) with a similar low dispersion (0.09 to 0.07).