C exhibits a great deal box [17]. The fabricated MEMS speaker or sputtered PZT
C exhibits considerably box [17]. The fabricated MEMS speaker or sputtered PZT thin films but distortion (THD)range of thicknesses, therefore Hz to eight kHz. scaling of diaphragms diaphragm also features a wider of less than 15 from 400 allowing the Even so, the acoustic within size was as largefor 20 mm 18 mm. restrictions as distinctive applications. Having a six mm diameter diaphragm, the fabricated Because the resonant frequency of a diaphragm is measured its cm and thickness, MEMS speaker accomplished a maximum SPL of 119 dB affected byat 1 region below a 10-Vpp scalingas shown in Figure 9a size calls for a thinner piezoelectric layer to retain a proper drive, down the diaphragm [16]. resonant frequency. In 2020,piezoelectric presentedwith higher piezoelectric constants have Furthermore, lead-free Wang et al. ceramics a piezoelectric MEMS speaker depending on thin ceramic PZT [16]. By using wafer bonding and chemical mechanical polishing also been explored for fabricating piezoelectric MEMS speakers. By way of example, in 2014, Gao approaches, ceramicpiezoelectric MEMS speakers 5using potassium sodium niobate et al. fabricated PZT was thinned down to only and applied to fabricate MEMS speakers. An3,optical image of the fabricated MEMS speaker along with a cross-section SEM image ((K,Na)NbO KNN)-based multilayer piezoelectric ceramics [77]. They employed a tape of the device layers are shown in applied Ag d alloys as an inner electrode. A schematic of casting and Sulfidefluor 7-AM In stock cofiring method and Figure 7a1,a2. Thin ceramic PZT not merely exhibits considerably higher piezoelectric constants than sol-gel or sputtered PZT thin films but additionally has a wider the multilayer ceramics based piezoelectric MEMS speaker in addition to a cross-section SEM image selection of thicknesses, thus permitting the scaling of diaphragms inside size restrictions for on the multilayer KNN-based ceramics are shown in Figure 7b1,b2, respectively. Having a distinctive applications. Having a 63mm diameter diaphragm, the fabricated MEMS speaker form issue of 23 27 0.six mm , employing 3 layers of 30-m-thick KNN-based ceramics, accomplished a maximum SPL of 119 dB measured at 1 cm below a 10-Vpp drive, as shown inside the fabricated MEMS speakers showed an typical SPL of 87 dB from 1 kHz to 20 kHz Figure 9a [16]. measured at three.16 cm below a 5-Vrms drive.Micromachines 2021, 12,Figure 7. Piezoelectric MEMS speakers according to new materials: (a1) optical image and (a2) cross-section SEM image of a Figure 7. Piezoelectric MEMS speakers depending on new materials: (a1) optical image and (a2) cross-section SEM image thin ceramic PZT-based MEMS speaker (Reproduced with permission from Taurine-13C2 Purity & Documentation Elsevier [16]); (b1) schematic and (b2) crossof a thin ceramic PZT-based MEMS speaker (Reproduced with permission from Elsevier [16]); (b1) schematic and (b2) cross-section SEM image of multilayer ceramics of a KNN ceramics-based MEMS speaker (Reproduced with permission from IOP [77]).Moreover, lead-free piezoelectric ceramics with higher piezoelectric constants have also been explored for fabricating piezoelectric MEMS speakers. For instance, in 2014, Gao et al. fabricated piezoelectric MEMS speakers employing potassium sodium niobate ((K,Na)NbO3 , KNN)-based multilayer piezoelectric ceramics [77]. They employed a tape casting and cofiring procedure and employed Ag d alloys as an inner electrode. A schematic of your multilayer ceramics primarily based piezoelectric MEMS speaker plus a cross-section SEM image on the multilayer KNN-based ceramics are shown in Figure 7b1,b2, respectively. Using a kind factor of 23 27 0.six mm3.