“…Because manufacturing processes are usually carried out at elevated temperatures, these UTs must also function at the required temperature. Various efforts have been devoted to the development of high temperature (HT) piezoelectric UTs [3][4][5][6][7][8][9][10][11]. Commercially, several HTUTs are also supplied by several companies, such as Etalon (Lizton, IN, www.etaloninc.com), Panametrics (Waltham, MA, www.panametrics.com), RTD (Rotterdam), Ultran (Boalsburg, PA, www.ultranlabs.com), Ishikawajima Inspection and Instrumentation Co. Ltd (IIICL, Tokyo) [7] etc.…”