[en] In this work, crystals of KY₃F₁₀ pure and doped with Yb, Nd and Tm were grown aiming at the attainment of blue emission via Tm³⁺ ions up conversion. It was established the best conditions to synthesis and purification of KY₃F₁₀ . Crystals doped with 1.3 mol% Nd, 0.5 mol% Tm and some concentrations of Yb (5, 10, 20, 30 and 40 mol%) were obtained by slow cooling of the charge from the melt, using an usual conventional synthesis system and in a reactive HF atmosphere. It was taken into account parameters as cooling rate and different configurations of boats to conditioning the materials. The limit of Yb concentration to obtain a unique cubic phase was determined as 30mol%, for the cooling rates used in this work. The physical and chemical characterizations of the samples were performed by X-ray diffraction, differential thermal analysis, inductively coupled plasma-optical emission spectroscopy (ICP-OES), scanning electron microscopy, optical absorption and emission. An initial spectroscopic study was performed to verify the effect of the Yb³⁺ concentration regarding the blue emission efficiency in the KY₃F₁₀ :Yb:Nd:Tm. When the Nd³⁺ is pumped at 797 nm, it was determined that the suitable Yb concentrations are between 10 and 20 mol% to obtain blue emission at 480 nm, and between 20 and 30 mol% to obtain emission at 450 nm. It was observed that two emissions bands in the UV (350 and 360nm) enhanced proportionally with the Yb³⁺ concentration. (author)