High Power (Na_0.5K_0.5)NbO₃-Based Lead-Free Piezoelectric Transformer

Abstract

Though there is a lot of research related with lead-free piezoelectric materials, high power characteristics of the candidate lead-free materials have not been looked into in the literature under equilibrium conditions. This paper reports high power characteristics of a sodium potassium niobate (NKN) based ceramic under equilibrium conditions, and its application as a candidate material for piezoelectric transformers compared with hard lead-zirconate-titanate (PZT). (Na 0:5 K 0:5 )(Nb 0:97 Sb 0:03 )O 3 was prepared with 1.5 mol % CuO addition. Disk-shaped samples were sintered with conventional sintering methods. High power characteristics were investigated with our high power piezoelectric characterization system (HiPoCS). Distinctly different from PZTs, the NKN ceramics did not exhibit a decrease in mechanical quality factor (Q m ) with increasing vibration velocity (up to 0.4 m/s). Ring-dot piezoelectric transformers made from a disk shaped NKN ceramic revealed power density as high as 25 W/cm 3 , almost comparable to that obtained for the conventional PZT transformers. In conclusion, NKN ceramics possess good high power characteristics, which are satisfactorily applicable to piezoelectric transformers. #

High Power Performance of Manganese‐Doped BNT‐Based Pb‐Free Piezoelectric Ceramics

“…The decrease in resonance frequency was due to the softening phenomenon as a result of evolution of domain walls, and hysteretic effects at high electric fields which results in energy dissipation and heat generation . A similar trend has been observed in other hard Pb‐free and Pb‐based ceramics . As depicted in Fig.…”

“…The mechanical quality factors of these materials at a vibration velocity of 0.2 m/s were reported to be around 800, 480, and 800, respectively. In addition, the heat generation and frequency shift with increasing the vibration velocity was inferior to Mn‐doped BNT‐based ceramics . High power performance of (Na 0.5 K 0.5 )NbO 3 , BaTiO3, and BNT‐based ceramics in Refs.…”

“…High power performance of (Na 0.5 K 0.5 )NbO 3 , BaTiO3, and BNT‐based ceramics in Refs. have only been measured up to a vibration velocity of 0.25 and 0.4 m/s, respectively.…”

Bulk piezoelectric ceramic transformers

“…Some of the lead free piezoelectric material compositions mostly based on doped (K 1/2 Na 1/2 )NbO 3 ceramics have been studied in the literature. [8][9][10][11][12] An interesting idea comes from Kozielski et al 13 in the 'ring dot' PT made from the composite of soft and hard PZT materials. The input circuit part of the PT body was made from hard PZT to allow the possibility of higher power driving in the input circuit.…”

Applications of Lead-Free Piezoelectrics

“…Ring-dot high-power transformers with 10.6 mm diameter  0.5 mm thickness were designed, manufactured, and characterized in terms of power density, equivalent impedance, and gain [12]. The picture and the design of the KNN ceramic ring-dot type transformer are shown in Fig.…”