Measurement of the lattice parameter of gadolinium gallium garnet crystals by the X-ray divergent-beam anomalous-transmission method

X-ray divergent-beam anomalous-transmission patterns of [111] Gd₃Ga₅O₁₂ crystal wafers cut from Czochralski-grown boules were obtained with Co radiation. The patterns contained {800} Kα transmission conics which just miss having a triple intersection. The intersection region was analyzed to determine the lattice parameter. The values of lattice parameter for wafers cut from several different boules ranged from 12.3807 to 12.383 Å with an estimated precision of ±0.0004 Å. The method is simple and non-destructive and offers sufficient precision to investigate compositional variations and to evaluate the crystals in terms of lattice parameter matching requirements for epitaxic film deposition.