Crystal growth and characterizations of a quartz-like material : GaPO4

This paper concerns the GaPO 4 crystal growth process which consists of an alternation of the vertical reverse temperature gradient (VTG) in sulfuric acid medium and the slow heating method (SHT) in phosphoric acid. Since this process is not usable at an industrial scale, we have investigated the crystal growth in phosphoric acid medium by VTG in order to find a direct way to synthetize GaPO 4 crystals. The as- grown crystals have been characterized by IR and NIR spectroscopies: the -OH content seems to decrease continuously without any plateau being observed at the last step of crystal growth as it was observed in berlinite. Moreover, both dielectric constants (e' T and dielectric loss (e'') have been studied in terms of temperature, frequency and -OH content. e' T 11 and e' T 33 have been found equal respectively to 6.2 and 6.6 at 20 o C and 50kHz