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The paper investigates the structure and crystallization specifics of glass behaving as a precursor of a pyroelectric material with a unique combination of properties of the composition 25La 2 O 3 × 25B 2 O 3 × 50GeO 2 depending on the quantity of Al 2 O 3 additive. It is established that as the alumina content grows, the crystallization of glass essentially changes: the propensity of glass to oriented surface crystallization of ferroelectric LaBGeO 5 is suppressed and the share of lanthanum borate and germanate grows. The type of crystallization of glass correlates with IR spectroscopy data, indicating that modifications of the glass structure caused by increasing Al 2 O 3 content lead to substantial changes in the BO 3 : BO 4 ratio.The physicochemical and crystallization properties of lanthanum-borogermanate (LBG) glasses [1 -5] give reason to attribute them to promising polar glass-ceramic dielectrics. The volume and surface crystallization of ferroelectric crystals LaBGeO 5 with the stillwellite-type structure provides for the development of surface and volume structure with nonlinear properties (optical, ferroelectric, pyroelectric, piezoelectric, etc.). The formation of LaBGeO 5 crystals in glass volume is considered by the authors of [1] as a model process of the formation of a nonlinear optical nano-and microcomposite medium. The formation of LaBGeO 5 crystals from LBG glasses at temperatures close to the vitrification temperature t g was observed in [4 -6]. At higher temperatures LBG glasses have clearly expressed oriented surface crystallization [2], which can lead to the formation of perfect textures. The LBG system has been used to produce nearly perfect textures of needle-shaped crystals of ferroelectric LaBGeO 5 with high pyroelectric activity [3] and also transparent surface layers of LaBGeO 5 crystals with nonlinear optical properties [4].The texture-forming capacity of different glass systems depends on many factors: glass compositions taking into account losses of component in volatilization, content of impurities, melting and cooling conditions, thermal conditions of crystallization etc., which had not been earlier investigated in detail [2,6]. Therefore, the reproducibility of microstructure and physical properties of textured glass ceramics, including the LBG system, remains rather low. The correlation between a glass composition and its texture-forming capacity is very complicated, which is well illustrated by the authors in [6] who observed the texture formation of ferroelectric Pb 5 Ge 3 O 11 in glasses of the PbO -GeO 2 system within a very narrow composition range. When a composition deviated from the optimal one within ± 0.3%, texture formation was almost totally suppressed. For other systems, data on the dependence of texture formation on the basic glass composition and additives introduced are missing.Knowledge of the specified factors is a necessary condition for controlled oriented crystallization of glasses allowing for forming polyfunctional textured materials [3,4,7].In our stud...