SI9600082A - Procedure of manufacture of mixture for pct elements - Google Patents

Abstract

The object of the invention is a process for making mass PTC elements where by adding a dopant to the improve the thermoelectric properties by two steps, such as breakthrough strength and varistor effect at the same time however, a lower specific resistance of the PTC can also be achieved element. The process for producing mass for PTC the elements according to the invention provide for the doping of the material into two stages. The dopant is added once before calcination, in the second stage, it is added before granulation. We use standard dopants when doping, but we can also use different dopants for each degree.

Description

PROCEDURE FOR MASS MAKING FOR PTC ELEMENTS

The subject of the invention is a process for producing mass for PTC elements, in which by adding a dopant in two stages, we improve thermoelectric properties such as breakthrough strength and varistor effect, and at the same time lower specific resistance of the PTC element can be achieved.

The invention belongs to the class H 01C 7/02 of the international patent classification.

A technical problem that is successfully solved by the present process is the determination of a mass production process for PTC elements according to which PTC elements will have better thermoelectric properties than those produced by existing processes.

The PTC element has a positive temperature coefficient, which means that as its temperature increases, its resistance decreases, until at some critical temperature the resistance increases sharply by several orders of magnitude (10 ⁴ to 10 ⁷ ). The basic material for making PTC elements is doped with BaTiO ₃ . The PTC effect is related to the polycrystalline nature of the ceramic and coincides with

Curie temperature BaTiO ₃ , the value of which can be shifted appropriately with the additives, thus shifting the PTC effect.

The standard process for the production of mass for PTC elements is based on the preparation of basic materials that are 45-85 mol% BaTiO ₃ , 1-2 mol% SrTiO ₃ , 5-20 mol%, CaTiO ₃ and 1-20 mol% PbTiO ₃ , and 0.1-0.3 mol% is a dopant (antimony, yttrium, niobium, lanthanum or cerium oxide). These ingredients must be prepared in powder form with a minimum of impurities. While agitated in agate ball mills, distilled water is added to the ingredients to maximize the homogeneity of the mass, which is then dried. Prior to granulation, manganese acetate, silica, and organic binders such as polyvinyl acetate, polyethylene glycol and others are added to the ground calcinate, followed by drying and spraying the granulate in a spray dryer. The granulate is formed in the process of dry compression into smaller tablets. Tool and force depend on the desired final dimensions of the finished product. The compressed tablets are then sintered in special tubs (heat treated at a temperature between 1300 and 1400 ° C) and then aluminum or silver electrode contacts (eg screen printing) applied to the sintered tablets and solidified at a temperature between 500 and 900 ° C.

The standard fabrication process involves doping the material with dopants such as antimony, yttrium, niobium oxide, etc. Doping is performed before calcination.

The object and object of the process of the invention is to provide a mass for PTC elements that will provide better thermoelectric properties than elements manufactured by existing processes.

According to the invention, there is provided a process for producing mass for PTC elements by doping the material in two steps. The dopant is added first before calcination and in the second stage it is added before granulation. For doping we use standard dopants using both the same dopant, but we can also use different dopants for the first and second doping.

In the described process of mass production for PTC elements by means of double doping, we improve the thermoelectric characteristics of the PTC element, especially the breakthrough voltage (by about 30%) and the Τ / ΔΙΙ ratio (reduces the varistor effect by about 20%), the PTC element made from the mass by the process according to the invention it also has a lower specific resistance and a higher penetration strength.

Figure 1 shows the l / U diagram of the PTC element. The curve denoting double doped material is indicated by the letter A.

Figure 2 shows the temperature dependence of the PTC element. Double doped material is marked with the letter A.

Claims (3)

5 1. A process for making a mass for PTC elements, in which the distilled water is added to the basic raw materials BaTiO ₃ , SrTiO3, CaTiO ₃ and PbTiO ₃ , and the dopant, prepared in the form of powder with a minimum of impurity, and then dried and then dried. Manganese acetate, io silica and organic binders such as polyvinyl acetate, polyethylene glycol and others are added before grinding calcined calcium, followed by drying and dispersing the granulate, dry pressing, sintering and contacting, characterized by doping the material is executed in two stages. 2. A method for producing mass for PTC elements according to claim 1, characterized in that 20 that the doping of the material in the first stage is performed before calcination, in the second stage before granulation. Method for producing mass for PTC elements according to claims 1 and 2, characterized in that different materials are used as dopants in each step.