Sapphire is a widely used material for optical, electronic and semiconductor applications due to
its excellent optical properties and very high durability. Optical and mechanical properties of
sapphire depend on many factors such as the starting materials that are used to grow crystals,
methods to grow sapphire crystals, etc. Demand for highest purity and quality of sapphire crystals
increased ten fold for the last several years due to new applications for this material.
In this work we studied the effect of starting materials and crystal growth methods on the optical
and mechanical properties of sapphire, especially concentrating on the effect of hydrogen on the
properties of sapphire.
It was found that the infrared (IR) absorption which is traditionally used to measure the hydrogen
content in sapphire crystals cannot be reliably used and the data obtained by this method
provides a much lower hydrogen concentration than actual. We have shown for the first time that
Nuclear Magnetic Resonance techniques can be successfully used to determine hydrogen
concentration in sapphire crystals.
We have shown that hydrogen concentration in sapphire can reach thousands of ppm if these
crystals are grown from Verneuil starting material or aluminum oxide powder. Alternatively, the
hydrogen concentration is very low if sapphire crystals are grown from High Purity Densified
Alumina (HPDA®) as a starting material. HPDA® is produced by EMT, Inc through their
proprietary patented technology.
It was found that optical and mechanical properties of sapphire crystals grown using EMT HPDA®
starting material are much better than those sapphire crystals grown using a starting material of
Verneuil crystals or aluminum oxide powder.
The NaTi2(P04)3 crystals were synthesised and their crystal structure and luminescence properties were investigated.
Two luminescence bands in green-orange and red spectral regions have been observed. Properties ofthe red emission of
the NaTi2(P04)3 crystals were investigated. Cumulative spectral data and their analysis have allowed to assign the red
band emission to luminescence ofthe Ti3+ ions, those are formed in the NaTi2(P04)3 crystals during growth.
Presented work reports the results of luminescence investigation of thermal treatment influence on the spectral properties of sulphate crystals. The alkali sulphate polycrystalline samples, obtained after annealing and melting, reveal significant photoluminescence, that is not practically observed at the similar conditions for the respective single crystals. Besides, luminescence character depends on the thermal treatment conditions. Changes in the concentration of various type of defects in crystal matrix must be expected under annealing of sulphate crystals at the certain temperatures. Increasing of concentration of some defects creates possibility to their observation by luminescence method. We have investigated absorption, excitation, photo- and x-ray luminescence spectra of alkali sulphate single crystals and powders.