Growth of piezoelectric crystals by Czochralski method

Abstract

The Czochralski method is one of the most widely used industrial technique to grow single-crystals, since it applies to a very large range of compounds, such as semiconductors, oxides, fluorides, etc... Many exhibit piezoelectric properties and some of them find applications in Surface-Acoustic-Waves or Bulk-Acoustic-Waves devices. That explains the large amount of work made on the development of the corresponding growth processes and the high levels of production achieved in the world today. We will review the basic principle, main features and parameters of the Czochralski method, and the configuration which is used by Crismatec. Then we will discuss in more details the growth parameters for the two piezoelectric crystals that we are producing, LiNb03 and LiTaO3, and present the state-of-the-art for both crystals : pulling axis, diameter and quality. We will also discuss some preliminary results on the growth of the new La3Ga5SiOlg langasite crystal.

Crystalline perfection, EPR, prism coupler and UV-VIS-NIR studies on Cz-grown Fe-doped LiNbO3: A photorefractive nonlinear optical crystal

“…During the growth process, a temperature gradient of $14 K cm À1 was maintained just above the melt level by RPGH to avoid the formation of extended structural defects like twins and grain boundaries which often occur at the early stage of crystallization from seed. 34 The starting 4 N purity (Sigma Aldrich) materials of LiNbO 3 and 0.05 mol% of Fe 2 O 3 were properly mixed and sintered at 1000 C for 8 h before melting. The melted charge was left for 4 h for homogeneous mixing of dopants.…”

Bulk Crystal Growth and Properties of a (K,Na)NbO3 Single Crystal by the Czochralski Method

“…K 2 CO 3 and Na 2 CO 3 were commonly used as self-flux in this method, which could prevent the introduction of impurity ions or atoms . However, the TSSG method presents shortages of small crystal sizes and low growth rates on KNN growth. , In contrast to adding fluxes, growing crystals directly from the original melt system is the most common approach for industrial-scale production of large-sized single crystals . For example, KNN crystals were successfully grown by the Bridgman and floating zone (FZ) methods. , However, the FZ method exhibits substantial fluctuations at the solid–liquid interface, and the crystal size is very limited, while the Bridgman method involves direct contact between the crystal and the crucible.…”

“…16,17 In contrast to adding fluxes, growing crystals directly from the original melt system is the most common approach for industrial-scale production of large-sized single crystals. 18 For example, KNN crystals were successfully grown by the Bridgman and floating zone (FZ) methods. 19,20 However, the FZ method exhibits substantial fluctuations at the solid−liquid interface, and the crystal size is very limited, while the Bridgman method involves direct contact between the crystal and the crucible.…”

Bismuth sodium titanate lead‐free piezoelectric coatings by thermal spray process

“…It is known that congruent crystallization materials have the same composition in liquid phase and solid phase as crystallized . Some congruent melting compositions, such as Bi 0.5 Na 0.5 TiO 3 , LiNbO 3 , and LiTaO 3 , are reported to be suitable for single crystal growth with proper compensation of the volatile loss to realize congruent crystalliztion . BNT‐based system is also one of the most promising lead‐free piezoelectric systems due to its high remnant polarization and large electromechanical coupling coefficient .…”