Abstract
The electrocaloric effect of ferroelectric materials can be used for refrigeration. This new method has the advantage of high efficiency, environmental protection and lower cost. Its variable size can satisfy the cooling requirements of different devices. However, it still exist some problems of lead-free ferroelectric ceramics refrigeration: its refrigeration temperature is less than 1 K; refrigeration temperature range is narrow; working temperature is either too high or too low. Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) material stands out and becomes the most promising candidate to replace lead-based materials. Properties of NBT almost meet the test requirements. Near depolarization temperature, this material shows ferroelectric/antiferroelectric phase transition, which brings a larger change in electric heating temperature. In this paper, electric card effect, lead-free piezoelectric ceramic materials and the BNT-xST ceramics were introduced in detail. Among these materials, BNT-xST is considered to be a promising material due to its excellent ferroelectric property and large electromechanical coupling coefficient.
Publisher
Darcy & Roy Press Co. Ltd.
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