JPS61186300A - Poling of single crystal - Google Patents

Abstract

PURPOSE:To shorten the treatment time, improve the productivity and decrease the production cost of a single crystal, by embedding an ingot crystal for growth in a heat-treatment container filled with fine powder of single crystal, and providing a platinum electrode along a specific crystal axis. CONSTITUTION:For example, an ingot 10 of LiNbO3 single crystal is embedded in fine crystal powder 5 of the same kind as the crystal to be grown, and filled in a treatment container 15. A pair of platinum electrode plates 6, 7 are placed opposite to the growing crystal axis 8 at the top and the bottom of the container. The annealing treatment and the poling treatment after anneal can be carried out continuously in the same furnace by the use of the above heat- treatment container. Accordingly, the complicate process of the annealing, etc. of grown ingot crystal can be simplified and the production steps can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a single crystal poling method for producing a single crystal for a piezoelectric vibrator, for example.

Piezoelectric vibrators convert electrical energy into mechanical energy.
Conventionally, there have been oscillators or resonators that utilize the piezoelectricity of the crystalline lens, but recently tantalum oxide (LiTaO3) and niobium oxide (aluminium niobium), which have a large electromechanical coupling coefficient, have been used.
Vibrators cut from piezoelectric crystals such as LiNbO3) are in public use.

The present invention relates to the production of single crystals such as LiNbO3.

Ingot distortion removal treatment (annealing), which is a process that precedes cutting to maintain the unique crystal axis of the grown crystal ingot body, and treatment to rearrange the crystal axis orientation (also called polarization treatment or poling treatment) - It shows concrete measures regarding.

[Conventional technology]

For example, a LiNbO3 single crystal ingot with a diameter of 8 cm and a height of 15 cm, grown by controlling the power of a high-frequency crucible furnace, is subjected to annealing and polarization treatment, followed by cutting out a crystal piece of a predetermined thickness and polishing the cross section of the cut out. Wafers are formed into vibrating element pieces.

FIG. 3 is a cross-sectional view of a processing container showing a conventional poling method in a furnace.

A single crystal ingot 10 set in a heat treatment container 15 made of alumina (Al103) is subjected to an annealing treatment and a poling treatment according to the following procedure.

(1) Annealing treatment at 1200°C (2) Cutting of both ends and flattening of the cut end faces 11 and 12 (3) Ceramic plate 13 and platinum electrode 14 for polarization treatment on the end faces 11 and 12 (4) At a furnace temperature of 1200° C., a current path of 0.2 A is caused to flow between the platinum electrodes 14 by the polarization power source 16 (current flow amount in terms of unit area = 40 μA/ct).

Such annealing (1) treatment or polarization treatment (4) may be caused by, for example, non-uniform temperature gradients in the Z-axis pulling crystal growth furnace.

It is also an indispensable means for correcting the disorder of the crystal arrangement within the ingono-IO grown as a result of minute fluctuations in the pulling speed.

However, the annealing process (1), the flattening process of the ingot end face (2), and the polarization process of the axial orientation arrangement (4) require a lot of time and effort, and there has been a demand for improvement in the poling process.

[Problems to be Solved by the Invention] Based on the above-mentioned key points, an object of the present invention is to simultaneously perform an annealing treatment for removing strain on an ingot body and a 9-polarization treatment to facilitate the process.

[Failure to solve the problem]

The problem lies in the poling treatment of grown ingot crystals placed in a heat treatment furnace. This problem is solved by the poling method of the present invention, which is performed by arranging electrodes.

[For production]

The heat treatment container filled with single crystal fine powder is stably attached to the growing ingot crystal body. That is, the flattening of the end faces of the ingot can be omitted, and the platinum electrodes attached to both ends of the grown crystal axis can be stably fixed.

In this way, annealing and post-annealing polarization treatment are performed continuously in the same heat treatment furnace, thereby improving the productivity of the flow.

〔Example〕

Two embodiments of polling processing according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a method for mounting a single crystal in a polling processing container, and FIG. 2 is a sectional view showing the same method for mounting a single crystal in another embodiment of the present invention.

In the drawings, the same reference numerals are given to the same components as those in the conventional structure to make the gist of the present invention clear.

The illustrated single crystal ingot 10 is, for example, a 1.1Nb03 single crystal whose material composition ratio weight is accurately controlled and which is pulled at an optimal growth rate.

1. The iNb○3 ingot 10 is embedded and installed in a processing container 15 filled with the same crystal fine powder 5 as the grown crystal, and flat platinum electrodes are placed on the upper and lower end surfaces facing the crystal axis 8 for growth. 6 and 7 are arranged.

The figure shows the arrangement of the platinum electrodes 14 during the poling process of the grown crystal 10 in the Z-axis direction (arrow 8).

The electrode 6 is a ring-shaped platinum electrode because the upper end 9 of the ingot 10 is conical.

The ingot 10 is not limited to having a flat lower end.

The bottom surface may be a curved surface, and in that case, a flat plate or a platinum electrode with an appropriately curved surface is attached to the electrode 7 side.

According to such a heat treatment container, annealing treatment and post-annealing poling treatment can be performed continuously in the same furnace. FIGS. 2A and 2B are both in the upright position shown in FIG. 1. Unlike when ingot mounting is done.

It shows a state in which the platinum electrodes 2 and 3 are placed in the horizontal direction and are used to perform annealing and poling on the crystal 10 grown in the Y-axis direction (arrow 4).

The crystal ingot 10 is stably mounted in a container 15 with the LiNbO3 fine powder 5 filled therein, together with the poling electrodes 2 and 3 provided facing each other in the Y-axis direction. After the single crystal 10 has been mounted, an annealing treatment for removing strain after growth and a poling treatment for rearranging the crystal orientation are continuously performed in the same heat treatment furnace.

In this way, the conventionally complicated processing such as annealing of grown ingot crystals is improved, and the number of production steps can be reduced.

〔Effect of the invention〕

As explained below-1-1, according to the single crystal poling method of the present invention, the crystal addition process after growth is substantially shortened.From this point of view, the single crystal poling method of the present invention increases productivity.

Therefore, it is effective in reducing the production costs of piezoelectric vibrators.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a method for mounting a single crystal in a heat treatment container according to the present invention. Are figures (a) and (b) of Fig. 2 other embodiments? ) [Cross-sectional view showing the crystal mounting method. FIG. 3 is a sectional view showing a conventional method for mounting a single crystal in a polling processing container. In the figure, 14 is the main axis (Y-axis) of the grown crystal. 8 is the main axis of the growing crystal (Zsuke). 5 is LiNh03 fine powder. 2.3, 6.7 and 14 are platinum electrodes. and 10 are grown crystals (Ingoso day.)

Claims (1)

[Claims] The poling treatment of the grown ingot crystal in a heat treatment furnace is characterized by burying the grown ingot crystal in a heat treatment container filled with single crystal fine powder, and arranging platinum electrodes along a certain crystal axis direction. Single crystal poling method.