Application of NTC thermistor in household appliances

Although NTC thermistors are usually invisible, these components play an indispensable role in the safety, stability and efficiency of household appliances. Do you know how many household appliances use NTC thermistor? You can take a look at the detailed list of the use of NTC thermistors in a typical urban family of three:


From the above table, it can be seen that NTC thermistors play a crucial role in modern household appliances. So, what is the working principle of NTC thermistors?

The Conductivity Principle of NTC Thermistor

The conductivity principle of NTC thermistor is a research outcome that has consumed a great deal of effort from researchers. In the early days, researchers theoretically speculated that the doping of transition metal oxides would cause structural changes, and the low-valent ions in the oxides would promote the transformation of the oxides into p-type semiconductors.

However, as research deepened, it was found that the conduction mode of such materials was not the mechanism of traditional semiconductor carriers moving throughout the entire band.

Currently, the recognized conduction mechanism of negative temperature coefficient NTC ceramic materials is based on the hopping conductivity model theory.

This theory reveals that the conduction of NTC thermistor ceramics is neither due to the movement of electrons in the conduction band nor the migration of holes in the valence band, but rather the direct transfer and transition of electrons between energy levels. To put it vividly, this is like electrons “jumping” between different atoms, from one atom to an adjacent one.

This process is closely related to the fact that most transition metals are variable-valence metals, and the transition of electrons is actually the valence change process of cations.

The Necessary Conditions for the Conduction of NTC Thermistor Ceramics

Based on the conduction mechanism of the hopping conduction model theory, we can summarize the necessary conditions for the conduction of spinel-structured NTC thermistor ceramics:

First, the ceramic material must be an inverse spinel or semi-inverse spinel structure;

Second, since the distance between the A B-site and another adjacent B-site cation is much smaller than the distance between adjacent A-site cations, electron transitions mainly occur between B ions. This requires that B sites must simultaneously have conductive ions of the same or different elements;

Third, B-site ions must be variable-valence ions. When these three conditions are met simultaneously, NTC thermistor ceramics can achieve conduction.

In addition, new research has found that the grain boundaries of NTC thermistor ceramics also have conduction capabilities, and this inference has been fully verified in practical applications. As a semiconductor sensitive ceramic, NTC thermistors have a resistance that decreases with increasing temperature, showing unique temperature-resistance characteristics.

The Characteristics and Applications of NTC Thermistor

The resistance range of NTC thermistors at room temperature is wide, ranging from 0.2Ω to 1MΩ, and the temperature coefficient is between -2% and -6%. With these different characteristics, they are widely used in various fields, such as temperature measurement, temperature compensation, and temperature sensing.

In temperature measurement and sensing, NTC thermistors, with their high sensitivity to temperature changes, accurately sense temperature and convert it into electrical signals, providing accurate basis for temperature control of equipment; in the field of temperature compensation, NTC thermistors can automatically adjust circuit parameters according to changes in environmental temperature, ensuring stable operation of electrical appliances under different temperature conditions.

As a leading player in the industry, Hefei minsing offers a series of high-precision and high-reliability NTC thermistor products. These products are suitable for various temperature sensing and control needs, and the company’s NTC temperature sensors are highly praised in the market for their excellent temperature control accuracy, good batch consistency, and long service life.