PZT material structure of quartet tungsten bronze

Tungsten bronze structure of piezoelectric ring transducer can be divided into many categories, of which the most common, the most piezoelectric sensor crystal is widely used, the most studied is the quartet tungsten bronze structure. Similar to the perovskite structure, the tungsten bronze structure is also formed by a total apex of oxygen octahedra. A total of the top of the BO6 oxygen octahedron coupled along the quaternary axis into a stack, the piles and then a total point in the form of connection. In contrast, it is the perovskite structure, these stacks of PZT material piezo disc do not align in a plane perpendicular to the quadruple axis, resulting in three different gaps: the A2, A1 and C positions of the pentagonal, quadrangular and triangular prism gaps. Among them A1 coordination number is 12, A2 is 15, C minimum is 9. At the same time, the oxygen octahedral center because of the location of symmetry is different, conical piezoelectric transducer is divided into B1 and B2 as for two octahedron center. This tungsten bronze structure can be written.These gap locations are generally occupied by ions that satisfy different size and valence requirements. In general, sites A1 and A2 are filled by larger Pb2 +, Ba2 +, Ca2 +, Sr2 +, Na +, K + and rare earth elements ions; while mini piezo ceramic discs can only be occupied by very small ions such as Li +, Be2 + and Mg2 + , Ta5 +, W6 +, Ti4 +, Zr4 + and Fe3 + ,which are filled in B1 and B2. Lead partial lead niobate (PbNb2O2) is the earliest discovered tungsten bronze ferroelectric, is also the first non-perovskite ferroelectric structure. The system has a high Curie temperature (570℃), high temperature mechanical transducer piezo is not easy to depolarization, large piezoelectric anisotropy d33 is mechanical quality factor of only 10 or so,high temperature ultrasonic transducers are suitable. However, the ferroelectric phase of partial lead niobate needs to be formed at around 1 230°C. Therefore, the preparation of lead niobate ceramics need to be more than 1 250 ℃ after the insulation,through the rapid cooling of pzt material piezo at temperature to maintain the stability of the ferroelectric phase, but due to the cracking of porcelain during the quenching process is often difficult to obtain dense lead metatitanate piezoelectric ceramics.