CRYSTAL-GROWTH AND CHARACTERIZATIONS OF QUARTZ-LIKE MATERIAL - GALLIUM PHOSPHATE (GAPO4)

This investigation concerns GaPO4 crystal growth in phosphoric and sul phuric acid media by the slow heating and vertical reverse temperature gradient methods. Systematic study of growth parameters shows that th e growth rate V-x is generally much greater than the other two, V-z an d V-y. The most interesting result is the ability to produce GaPO4 epi taxy on large berlinite seeds in sulphuric acid and to use them for Ga PO, crystal growth in phosphoric acid where the V-x/V-z ratio can be c lose to 1. As for alpha-quartz and berlinite, V-y growth rate being al ways very slow, the lengthening of these crystals in that direction is obtained by the use of several joined seeds accurately adjusted and s pliced on a quartz plate. The epitaxial fit and the crystalline qualit y have been checked by X-ray topography. The OH content, determined by infrared and near infrared spectrometry, proves a lower OH concentrat ion than in the case of berlinite when approximately the same crystal growth conditions are used. Piezoelectric characterizations of resonat ors have been suitable to specify the AT-cut position, its very promis ing piezoelectric properties with a high thermal stability and a Q fac tor are already nearly sufficient for applications. The most interesti ng properties of these crystals, the piezoelectric properties, are com pared with those of other known crystals, quartz and berlinite, and re lated to their crystal structure distortions. The observed evolution a llows the prediction of some interesting unknown characteristics for o ther quartz-like materials.