标题：High temperature ReCOB piezocrystals: Recent developments
作者：Shujun Zhang;Fapeng Yu;Ru Xia;Yiting Fei;Eric Frantz;Xian Zhao;Durong Yuan;Bruce H.T. Chai;David Snyder;Thomas R. Shrout
作者机构：[Zhang, S] Materials Research Institute, Pennsylvania State University, University Park, PA 16802, United States;[ Yu, F] Materials Research Institute 更多
会议名称：16th International Conference on Crystal Growth (ICCG16)/14th International Conference on Vapor Growth and Epitaxy (ICVGE14)
会议日期：AUG 08-13, 2010
来源：Journal of Crystal Growth
关键词：A1. Characterization;A2. Czochralski method;B1. Borates;B2. Piezoelectric materials
摘要：Piezoelectric sensors for high temperature applications have attracted attention due to their simplistic structure, fast response time and ease of integration. In this article, oxyborate ReCa_4O(BO_3)_3 (Re: rare earth element; abbreviated as ReCOB) piezoelectric crystals were surveyed for their potential use in high temperature sensing applications. In contrast to quartz and GaPO_4 crystals, no phase transformation(s) are observed prior to their melting points, being in the order of～1500℃. The electrical resistivity, dielectric, piezoelectric properties and resonance-impedance characteristics were studied as a function of temperature over the range of Room Temperature (RT) to 950℃. The resistivity of ReCOB was found to be～2 ×10~8 Ohm cm at 800℃, two orders higher than langasite, another widely studied crystal system. The electromechanical coupling factors k_(26) and piezoelectric coefficients d_(26) were found to be > 20% and >10pC/N, respectively, with the variation being ≤20% over the studied temperature range. The resonance frequency for width shear vibration was found to decrease linearly with increasing temperature for YCOB crystals, with the Temperature Coefficient of Frequency (TCF) in the order of 70 ppm/K, while for NdCOB crystals, a nonlinear behavior was observed, demonstrating a potential zero TCF crystal cut. The high resistivity, high piezoelectric properties and low mechanical and dielectric losses, together with temperature independent characteristics, demonstrate that oxyborate crystals are promising candidates for high temperature sensing applications.