For real-world applications, temperature stability of the functional properties is as important as all the other physical properties. In this regard, piezoelectric applications are firstly classified in terms of required temperature regime and summarized in Table 3. Next, each category is sub-divided into resonance and non-resonance applications. It is noted that a piezoelectric device is a translator between mechanical and electrical energy. Thus, the electromechanical coupling coefficient isessential for the assessment of piezoelectric materials, especially when driven in resonance modes. Simultaneously, mechanical displacements and electric charge are also proportional to themechanical quality factor for a piezoelectric device driven in resonance state. Therefore, the product of mechanical quality factor(Qm) and square of electromechanical coupling coefficient (k2)is usually taken as the key evaluation factor for applications in resonance modes. In this table vmaxstands for maximum vibra-tion velocity without loss in piezoelectric properties due to heat