I. Introduction
Langasite-Type single crystals without phase transitions up to the melting point are piezoelectric materials that can be applied for high-temperature sensor devices [1]–[4]. The melting point of these materials is greater than 1000°C, and their piezoelectric constants are two to three times greater than those of quartz up to 1000°C. Therefore, it is expected that these langasite-type crystals could be used in combustion sensors in car engines with an operating temperature limit of 400°C [5], [6]. However, wide application of such sensors in automotive industry is currently impossible because of the high cost of manufacturing. In general, langasite-type crystals are grown by the Czochralski (Cz) method as large bulk crystals of several inches in diameter. The cost of the subsequent cutting and polishing of the starting bulk crystal to create the sensor elements directly affects the final price of the combustion sensor. In addition, approximately 20% to 50% of the starting materials is not consumed when the Cz growth is completed, and these substances must be removed from the crucible before it can be reused.