The ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices, and for the coupling of light absorption with other functional properties [1-7]. In these materials, the strong inversion symmetry breaking that is due to spontaneous electric polarization promotes the desirable separation of photo-excited carriers and allows voltages higher than the band gap, which may enable efficiencies beyond the maximum possible in a conventional p–n junction solar cell [2, 6, 8-10]. Ferroelectric oxides are also stable in a wide range of mechanical, chemical and thermal conditions and can be fabricated using low-cost methods such as sol–gel thin-film deposition and sputtering [3, 5]. Recent work [3, 5, 11] has shown how a decrease in ferroelectric layer thickness and judicious engineering of domain structures and ferroelectric–electrode interfaces can greatly increase the current harvested from ferroelectric absorber materials, increasing the power conversion efficiency from about 10^-4 to about 0.5 per cent. Further improvements in photovoltaic efficiency have been inhibited by the wide bandgaps (2.7–4 electronvolts) of ferroelectric oxides, which allow the use of only 8–20 per cent of the solar spectrum. Here we describe a family of single-phase solid oxide solutions made from low-cost and non-toxic elements using conventional solid-state methods:[KNbO₃]_1-x[BaNi_1/2Nb_1/2O₃2d]_x (KBNNO). These oxides exhibit both ferroelectricity and a wide variation of direct bandgaps in the range 1.1–3.8 electronvolts. So, because KBNNO shows new electronic properties and abrupt band changes when doped, we went to check how what are the influences of high pressures on this new material. Thus, the phase evolution under high extreme conditions (pressure and temperature) was investigated on samples submitted to the quasi hydrostatic pressure (at 7,7 GPa) in a toroidal press and sintered at 1500 ºC from 15 min. The structural properties were investigated by XRD and Raman spectroscopy measurements performed ex situ. The results show transitions phase in lower nominal pressure that of the KNbO₃ matrix [12].

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