Optical Properties of Al- and Zr-Doped Rutile Single Crystals Grown by Tilting-Mirror-Type Floating Zone Method and Study of Structure-Property Relationships by First Principle Calculations

Table 2

Comparison of direct and indirect band gaps energies (eV) and symmetry of the valance to conduction band transition for rutile TiO₂, Al-doped rutile, and Zr-doped rutile.

Valance to conduction band transition	Band gap energies (eV)
	TiO2	Al : TiO2	Zr : TiO2
	1.8805	1.9411	1.8529
–Z	2.8656	3.0882	2.9117
–R	1.9701	2.1176	1.9411
–M	1.9701	2.1176	1.9411
X–X	3.2238	3.3529	3.1764
R–R	2.8656	3.0882	2.9117
Z–Z	4.2985	4.4117	4.4117
M–M	2.8546	3.0882	2.9117
A–A	3.2238	3.3529	3.2647