Structural and optical properties of NdxGd1−xCr3(BO3)4 solid solutions E.A. Dobretsova, K.N. Boldyrev, E.Yu. Borovikova and V.A. Chernyshev EPJ Web Conf., 132 (2017) 03012 Published online: 13 December 2016 DOI: 10.1051/epjconf/201713203012