Anisotropic thermal expansion of stoichiometric lithium niobate crystals grown along the normal direction of facets
✍ Scribed by Xuewu Xu; Tow-Chong Chong; Sanjeev Solanki; Xinan Liang; Shaoning Yuan
- Publisher
- Elsevier Science
- Year
- 2004
- Tongue
- English
- Weight
- 575 KB
- Volume
- 26
- Category
- Article
- ISSN
- 0925-3467
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✦ Synopsis
In this paper, a stoichiometric lithium niobate (SLN) crystal with the size up to 20 • 20 • 18 mm 3 was grown along the normal direction of the (0 1 2) facet from the 16 mol% K 2 O fluxed melt by the top-seeded solution growth method. The anisotropic thermal expansion of the SLN crystal and congruent lithium niobate (CLN) crystal was measured along different directions by using a Shimadzu thermomechanical analyzer. As compared with CLN, the SLN crystal exhibited slightly larger thermal expansion along the Z-axis and slightly smaller expansion along the X -axis. Both the SLN and CLN crystals showed strong anisotropy in the thermal expansion. The thermal expansion coefficient of SLN along the X -axis ($16.7 • 10 À6 °CÀ1 at 300 °C) is much larger than that along the Z-axis ($2.5 • 10 À6 °CÀ1 at 300 °C). Based on the experimental data and polynomial fitting results, we calculated the thermal expansion coefficients for different directions. In the case of growing the SLN crystal along the normal direction of (0 1 2) facet, we studied the radial anisotropic thermal expansion and discussed the cracking problem of the crystal according to its actual growth morphology. It is found that the cracks of SLN can be suppressed by growing the crystal along the W -axis due to its reduced radial anisotropy in the thermal expansion.