High-Curie-point low-resistivity lead-free PTCR (Positive Temperature Coefficient of Resistance) ceramic material and preparation method thereof

Abstract

The invention discloses a high-Curie-point low-resistivity lead-free PTCR (Positive Temperature Coefficient of Resistance) ceramic material with a constitution formula (1): [Bi0.5(Na1-xKx)0.5]y[Ba1-y-z-j]TiO3+zLn3++jCn2++kSi2++wMn(NO3)2. In the formula, x is equal to 0.1-0.5, y is equal to 0.1-0.3, z is equal to 0.001-0.01, j is equal to 0.1-0.2, k is equal to 0.01-0.05, w is equal to 0.0001-0.001, Ln comprises one or two elements of Sm, Nd, Y and La, and Cn comprises at lest one of Ca and Sr. The preparation method comprises the following steps of: (1) respectively preparing solutions containing Bi, Na, K, Ba, Ti, Ln, Cn, Si and Mn ions and preparing a mixed solution according to a mol ratio given in formula (1); (2) mixing the mixed solution, organic monomers and a crosslinking agent according to a proportion of 100ml: (6-20)g: (0.5-8)g and crosslinking and polymerizing the organic monomers and the crosslinking agent in the solution to obtain gel; (3) calcining at 700-800 DEG C for 1-3h to obtain ceramic powder; and (4) granulating the powder, drily pressing to form and calcining at a high temperature of 1200-1300 DEG C for 1-2h. The ceramic material has the advantages of high Curie point and low resistivity.

Description

technical field [0001] The invention belongs to the technical field of functional ceramic materials, in particular to a BaTiO 3 The invention discloses a lead-free PTCR ceramic material with a high Curie point and low resistivity and a preparation method thereof. Background technique [0002] PTCR generally refers to a thermistor material or component with a positive temperature coefficient. A typical PTCR material is a semiconductor ceramic material based on barium titanate. Its characteristic is that when the ambient temperature rises to a certain temperature (Curie point or switch temperature point), its resistance value will increase by several orders of magnitude. Using this material as a heating body, its heating power hardly changes with the change of the applied voltage, so it has the function of automatic constant temperature. At the same time, it is widely used in industrial and military electronic equipment, as well as household appliances and other fields becau...

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Problems solved by technology

The above-mentioned materials have high resistivity, small lift-to-drag ratio, and poor overall PTC effect, which cannot meet the technical requirements of low-voltage applications (such as low-voltage electrical appliances such as automotive air conditioners)

[0005] Generally all adopt traditional solid phase sintering method (comprising Chinese invention patents such as above-mentioned CN10128473A, CN 101284731A) aspect preparation technology, in initial mixing, generally all adopt deionized water as medium to carry out wet ball milling, because sodium salt belongs to Water-soluble salts can easily cause the loss of sodium ions during the ball milling process, resulting in the deviation of the chemical ratio of the material

At the same time, due to the high synthesis temperature (about 1000°C), the Bi element is extremely volatile, which will also lead to deviations in the chemical ratio of the material.

For perovskite (ABO 3 ) structure (Bi 0.5 Na 0.5 ) x (Ba 1-x )TiO 3 Due to the loss of sodium ions and the volatilization of Bi elements, a large number of A-site ion vacancies will be generated, as a result, high-concentration acceptor impurities will be formed, which will affect the semiconductorization of materials, and it is difficult to obtain PTC materials with low resistivity.

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