Optical, mechanical, and thermal properties of nonlinear LiKB 4 O 7 crystals
- PDF / 196,976 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 65 Downloads / 222 Views
ICAL PROPERTIES OF CRYSTALS
Optical, Mechanical, and Thermal Properties of Nonlinear LiKB4O7 Crystals V. T. Adamiv Institute of Physical Optics, Lviv, 79005 Ukraine e-mail: [email protected] Received February 26, 2007
Abstract—Nonlinear LiKB4O7 single crystals have been grown by the Czochralski method from a stoichiometric melt. The optical, acoustic, piezo- and electro-optical, and thermal properties of these single crystals have been studied. PACS numbers: 78.20.Ci, 78.20.Ek, 78.20.Hp, 78.20.Jq DOI: 10.1134/S1063774508030176
Anhydrous borate single crystals (e.g., LiB3O5, Li2B4O7, and β-LJÇ2é4) proved to be materials with high radiation hardness, used for the generation of higher harmonics of laser radiation in a wide spectral range up to the far UV [1, 2]. Recent extensive studies of anhydrous borate single crystals showed that they can be used in other areas of optoelectronics. In particular, these crystals may be promising as acousto-optical [3] and birefringent materials for passive optical elements. Therefore, further wide investigation of their physical properties remains urgent. The aim of this work was to grow and study the properties of LiKB4O7 single crystals. The transparency range; refractive indices; acousto-, piezo-, and electro-optical; and thermal properties of a LiKB4O7 crystal were investigated. THE METHOD FOR GROWING LiKB4O7 SINGLE CRYSTALS The compound under study belongs to the sp. gr. P212121. The unit-cell parameters of a LiKB4O7 crystal are as follows: a = 8.4915 Å, b = 11.1415 Å, and c = 12.6558 Å; the unit cell contains 104 atoms; the density is ρ = 2.19 g/cm3. LiKB4O7 melts congruently at Tm ~ 680°ë [4, 5].
Solid state synthesis of the growth charge for LiKB4O7 was stopped after reaching a temperature of 650°ë. The synthesis was completed at a temperature ≤800°ë during build up and homogenization of the melt in a Pt crucible with sizes of 40 × 40 mm2. A LiKB4O7 single crystal was grown by the Czochralski method using a single-crystal seed oriented along the [010] crystallographic axis [8]. The validity of the obtained LiKB4O7 material was confirmed by X-ray analysis (Fig. 1) using synchrotron radiation of the DORIS accelerator at the Deutsches Elektronen Synchrotron (DESY) (Hamburg, Germany). Pulling rates in the range 0.1–0.3 mm/h and seed rotation rates from 3 to 5 rpm were found to be optimal basic parameters for growing LiKB4O7 single crystals. The grown LiKB4O7 single crystals of good optical quality were ~20 mm in diameter and 10–15 mm in length. To minimize the growth stress in the LiKB4O7 single crystal, the rate of postgrowth cooling to room temperature did not exceed 50 K/h, which follows from the analysis of the temperature dependences of the coefficients of linear thermal expansion (CLTEs).
The charge for growing LiKB4O7 single crystals was obtained by multistep solid-state synthesis [6, 7] from Li2ëé3 and K2ëé3 carbonates and boric acid ç3Çé3 with a high degree of purity. Generally, the synthesis process can be described by the chemical equation
I, rel. units
INTRODUC
Data Loading...
