Platinum and palladium high-temperature transducers on langasite
Platinum and palladium high-temperature transducers on langasite
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DOI：
10.1109/tuffc.2005.1428035
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发表时间：
2005-05
期刊：
影响因子：
--
通讯作者：
J. Thiele;M. P. da Cunha
中科院分区：
文献类型：
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作者：
J. Thiele;M. P. da Cunha
目前迫切需要制造能够在恶劣环境、高温高压或高功率条件下工作的表面声波（SAW）器件。这些SAW器件可作为频率控制元件、信号处理滤波器、压力、温度和气体传感器。应用包括天然气和油井，通信系统中的大功率双工器，以及汽车和航空航天内燃机。在这些可以达到几百摄氏度的高温和功率操作条件下，典型制造的铝（Al）薄膜数字间换能器（IDT）由于电和应力迁移而失效。本文报道了在langasite （LGS）压电衬底上设计、制造和测试的高温SAW换能器。铂（Pt）和钯（Pd）（熔点分别为1769/spl℃和1554.9/spl℃）被用作SAW IDTs的金属薄膜。锆（Zr）最初被用作SAW换能器上的粘附层，以避免迁移到Pt或Pd金属膜中。作为制造SAW器件的衬底的压电LGS晶体，在熔点为1470/spl℃之前没有表现出任何相变。设计并构建了一个能够承受1000/spl度/C的射频（RF）测试和表征系统。使用Pt和Pd电极的LGS SAW器件和测试系统在长达6周的时间内暴露在250/spl℃至750/spl℃的温度范围内，与室温相比，SAW器件在传输系数（|S/sub 21/|）量级上的退化程度优于7 dB。这些结果使Pt和Pd LGS SAW idt能够在恶劣环境中用于上述现代应用。
There is a pressing need for the fabrication of surface acoustic wave (SAW) devices capable of operating in harsh environments, at elevated temperature and pressure, or under high power conditions. These SAW devices operate as frequency-control elements, signal-processing filters, and pressure, temperature , and gas sensors. Applications include gas and oil wells, high-power duplexers in communication systems, and automobile and aerospace combustion engines. Under these high-temperature and power-operating conditions, which can reach several hundred degrees centigrade, the typically fabricated aluminum (Al) thin film interdigital transducer (IDT) fails due to electro and stress migration. This work reports on high temperature SAW transducers that have been designed, fabricated, and tested on langasite (LGS) piezoelectric substrates. Platinum (Pt) and palladium (Pd) (melting points at 1769/spl deg/C and 1554.9/spl deg/C, respectively) have been used as thin metallic films for the SAW IDTs fabricated. Zirconium (Zr) was originally used as an adhesion layer on the fabricated SAW transducers to avoid migration into the Pt or Pd metallic films. The piezoelectric LGS crystal, used as the substrate upon which the SAW devices were fabricated, does not exhibit any phase transition up to its melting point at 1470/spl deg/C. A radio frequency (RF) test and characterization system capable of withstanding 1000/spl deg/C has been designed and constructed. The LGS SAW devices with Pt and Pd electrodes and the test system have been exposed to temperatures in the range of 250/spl deg/C to 750/spl deg/C over periods of up to 6 weeks, with the Saw devices showing a reduced degradation better than 7 dB in the magnitude of transmission coefficient, |S/sub 21/|, with respect to room temperature. These results qualify the Pt and Pd LGS SAW IDTs fabricated for the above listed modern applications in harsh environments.