24The accurate determination of Li isotopic ratios by MC-ICP-MS has traditionally 25 been hampered by high background and severe memory effect of Li. In this study, a 26 novel method to efficiently reduce the high background and memory effect of Li was 27 developed. It was found that the Li background can be significantly reduced by a factor 28 of 15 to 70 by using a 5% NaCl rinse solution. In addition, the "mismatching effects" 29 reported previously which are caused by different acid and Li concentrations between 30 the sample and standard, were eliminated once the Li background was efficiently 31 reduced, suggesting that the crux of the two types of matrix effects is actually the high 32 Li instrumental background and memory effect. Applying the background reduction 33 technique, a method without strict matrix-matching was developed for the accurate and 34 precise determination of Li isotopic ratios. The proposed method was validated by 35 analysis of eight reference materials with satisfying results, even when Li concentration 36 in the samples were not matched with that of standards. The external precision of this 37 method is better than ± 0.25‰ (2SD) for δ 7 Li, suitable for the identification of small 38 fractionation of Li isotopes occurred in geological processes. With the proposed method, 39 there is no need to match the Li and acid concentration of sample and standard, 40 significantly reduced sample preparation time and increased sample throughput. 41 Key words: Lithium isotopes; MC-ICP-MS; Memory effect; Matrix effect; Silicate 42 references; Seawater. 43 44

A novel inertial piezoelectric actuator is proposed in this study to address the large vibration problem in piezoelectric actuators with a typical cantilever structure. Piezoelectric vibrators with a two fixed-end beam structure were designed as driving elements to improve the precision and stability of the proposed actuator. Simulation and experiments were performed to evaluate the vibration model of the vibrators. A series of experiments was conducted to evaluate the performance of the presented actuator with regard to its linearity, repeatability, and output stepping. Angular resolution can reach 0.453 μrad at 36 V, 40 Hz, and 600 g load. Under the conditions of 40 V, 40 Hz, and 400 g load, repeatability reaches 0.0024 mrad with a maximum deviation of 0.007 mrad. Experimental results show that the designed actuator can achieve high precision and high stability under load conditions. This novel actuator has a reference value and significance in practical applications that require microdisplacement.

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