Abstract
Content
- 1. Actuality of theme
- 2. Purpose and objectives of research
- 3. Manufacturing piezoceramic products
- References
1. Actuality of theme
Piezoceramic products find a wide use in the different areas of national economy: in a radioelectronic technique, acoustics, ultrasonic transformers, to medicine of and other. However, as far as expansion of profile of the user equirements grew and toughen requirements to it, that predetermined the improvement of technology of production along with the search of new compositions.
There is a great number of factors participating in forming ofstructure-sensitive properties. Finding out of their role andintensification of technology with the purpose of improvement рiezoceramic’s parameters is important and actual problem.
2. Purpose and objectives of research
Purpose – studying of the influence of some technological factors on the electrical properties of PZT piezoelectric ceramics technology to optimize manufacturing. In this case solves the following tasks:
- 1. To study influence of composition of the plumbiferous filing up and method of packing of wares at their using on properties of piezoelectric elements.
- 2. To investigate the dependence of properties on the type of pressing, sintering temperature and microstructure of the ceramics.
- 3. To establish the relationship between the type of modifier in the composition and sintering conditions.
- 4. To find out the role of sintering atmosphere on the formation of the service characteristics of piezoelectric elements with different methods of sample preparation.
- 5. Identify ways to optimize the production technology of piezoelectric elements.
3. Manufacturing piezoceramic products
Ceramic ferroelectrics include barium titanate, and a number of solid solutions based on it, solid solutions metaniobate lead and barium titanate and solid solutions of lead zirconate titanate and lead others.
A feature of these materials is that, than after exposure to a constant electric field, they are piezoelectric (piezoceramic) and can be used as electromechanical transducers. Details of the ferroelectric is a product of various geometric shapes: cylinders, discs, prisms, hollow spheres, etc.
For the manufacture of ferroelectric ceramics are usually used carbonates and oxides of the metals [1].
Raw materials made in the required amounts were mixed and subjected to fusionat certain temperatures. Obtained after the synthesis of the material milled, plasticized and make out detail in the triangle, find the correct form. Decorated parts are subjected to repeated heating, which occurs during the sintering of mineral particles and the formation of polycrystalline structure [2].
After machining to the required dimensions on the parts of the ferroelectric electrodes are applied by brazing, and then polarize their constant high voltage.
Manufacturing process involves mixing and fine grinding of all compounds in a vibrating mill. Simple design vibrating mill, low cost and compact to incorporate them into existing production lines without entering additional areas.
Fine grinding in a vibrating mill is the most common way to increase the surface of a solid body with the environment. In addition, the fine grinding dramatically increases the number of free particles. These circumstances lead to increased activity of solids as a structure-forming materials, and significantly speed up the dissolution, sintering, phase and chemical transformations.
In the absence of vibration mill, and especially in the laboratory allowed the use of ball mills for grinding and mixing the wet method.
Before making ceramic material to a part of it is administered plasticizers. As the latter can be used an aqueous solution of polyvinyl alcohol, paraffin, wax, dextrin, and others [2].
The use of a plasticizer is determined by the geometrical shape, size, details and method of design. So, when you make a part of simple geometric forms (disks, cylinders, prisms, etc.) of the quality of the plasticizer is expedient to use 3-6% aqueous solution of polyvinyl alcohol. In the manufacture of parts with complex geometry (hollow spheres, cones, etc.) subjected to mechanical treatment in the unfired state, as a plasticizer used paraffin. This plasticizer is mixed with oleic acid, or hot wax is used in injection molding.
The process of registration details can be carried out by different methods: dry pressing, hot casting under pressure and in some cases pulling through the mouthpiece [3].
Each of the above methods of design detail has its advantages and limitations. The most productive and easy to implement in the production of a semi-dry pressing, but it is applicable only for simple geometric forms.
Hot molding can make out the details of any geometrical shape, but due to the need to introduce an additional operation in the process of burning, a plasticizer, increases the production cycle for 70-80 h and requires an additional furnace units, which limits the possibility of applying this method in production.
The method of pulling the mouthpiece appropriate to apply only to decor cylindrical details of small diameter (3-5 mm). The final firing is the most important technological details of the operation, during which the formation of a monolithic body, called ceramic crock [2].
The condition for obtaining high-quality details is right to blow, even heating at a certain speed before the temperature and holding at this temperature.
The firing temperature depends on the type and amount of impurities present in the starting materials. The heating time and holding time at maximum temperature is determined not only by the composition and technologypreparing molding powders, but the size of parts, as well as the size of cages.
The heating rate is not advisable to use above 150 °C per hour, and the cooling rate, within the 150-200 °C in an hour or cooled in the furnace (in the case of firing in the kiln chamber.) The exceptions are the large-baritnye parts with wall thickness exceeding 15 mm, the heating rate which, as well as the cooling rate should not exceed 50-60 °C per hour.
The above design methods can
not provide details of the ferroelectric desired geometric shape and
size specified. This problem is solved by means of machining parts
(blanks) in the
crude
(unfired) and fired
states. In the unfired state usually mechanically processed Pressed
blanks in order to give them the desired geometric shape, getting a
different method is not feasible.
Machining of fired ceramic parts or blanks can be produced by grinding or turning on machine tools.
Very important is the mechanical strength of cohesion of silver electrodes with a surface of ceramic parts. The highest value of this strength is achieved by careful degreasing machined parts, carrying out sanitary and technical requirements in the process of applying silver paste, and subject to temperature brazing of silver in the ceramics [3].
The final operation of the process is the polarization components of high voltage direct current.
Polarization can be conducted at normal temperature and at a temperature close to the Curie temperature of the composition. A more rational method is the second polarization. Significant factors in this process are the preparation of parts for the polarization (careful of cleaning and degreasing), the medium polarization and the heating of the parts in the case of the polarization in the hot state [3].