An ultrasonic transducer , comprising: a piezoelectric composite layer configured to be in acoustic communication with a sample and having at least partially decoupled acoustic impedance and electrical impedance properties, the piezoelectric composite layer comprising: an array of spaced-apart piezoelectric regions , each spaced-apart piezoelectric region being made from a piezoelectric material having a first acoustic impedance and a first electrical relative permittivity; a filler material positioned between adjacent spaced-apart piezoelectric regions , the filler material comprising a polymer matrix having a second acoustic impedance and a second electrical relative permittivity, the second acoustic impedance being smaller than the first acoustic impedance, and the second electrical relative permittivity being smaller than the first electrical relative permittivity; and a non-piezoelectric material in contact with the polymer matrix , the non-piezoelectric material having a third acoustic impedance and a third electrical relative permittivity, the third acoustic impedance being greater than the second acoustic impedance, and the third electrical relative permittivity being smaller than the first electrical relative permittivity; and one or more electrodes in electrical communication with the piezoelectric composite layer , characterized in that : the polymer matrix is made from epoxy and the non-piezoelectric material is hafnium oxide powder. a piezoelectric composite layer configured to be in acoustic communication with a sample and having at least partially decoupled acoustic impedance and electrical impedance properties, the piezoelectric composite layer comprising: an array of spaced-apart piezoelectric regions , each spaced-apart piezoelectric region being made from a piezoelectric material having a first acoustic impedance and a first electrical relative permittivity; a filler material positioned between adjacent spaced-apart piezoelectric regions , the filler material comprising a polymer matrix having a second acoustic impedance and a second electrical relative permittivity, the second acoustic impedance being smaller than the first acoustic impedance, and the second electrical relative permittivity being smaller than the first electrical relative permittivity; and a non-piezoelectric material in contact with the polymer matrix , the non-piezoelectric material having a third acoustic impedance and a third electrical relative permittivity, the third acoustic impedance being greater than the second acoustic impedance, and the third electrical relative permittivity being smaller than the first electrical relative permittivity; and an array of spaced-apart piezoelectric regions , each spaced-apart piezoelectric region being made from a piezoelectric material having a first acoustic impedance and a first electrical relative permittivity; a filler material positioned between adjacent spaced-apart piezoelectric regions , the filler material comprising a polymer matrix having a second acoustic impedance and a second electrical relative permittivity, the second acoustic impedance being smaller than the first acoustic impedance, and the second electrical relative permittivity being smaller than the first electrical relative permittivity; and a non-piezoelectric material in contact with the polymer matrix , the non-piezoelectric material having a third acoustic impedance and a third electrical relative permittivity, the third acoustic impedance being greater than the second acoustic impedance, and the third electrical relative permittivity being smaller than the first electrical relative permittivity; and one or more electrodes in electrical communication with the piezoelectric composite layer , characterized in that : the polymer matrix is made from epoxy and the non-piezoelectric material is hafnium oxide powder. <EOS>