Abstract: Aspects include a method for treating a polycrystalline material, the method comprising: exposing a surface of the polycrystalline material to a plasma thereby changing the surface of the polycrystalline material from being characterized by a starting condition to being characterized by a treated condition; wherein: the surface comprises a plurality of crystallites each having the composition MB6, M being a metal element; the plasma comprises ions, the ions being characterized by an average ion flux selected from the range of 1.5 to 100 A/cm2 and an average ion energy that is less than a sputtering threshold energy; the starting condition of the surface is characterized by a first average work function and the treated condition of the surface is characterized by a second average work function; and the second average work function is less than the first average work function.